Car Audio Forumz - The #1 Car Audio Forum - Much needed clarification on highs/tweeters/crossovers

I am hoping that somebody will be able to help as I have been having an on going issue for over a year with my highs in my car sounding too loud and giving off that chhh/shhhh sound.
I will give you a FULL breakdown of everything that has happened. (Sorry if i jump around a bit. there is a lot of info to cover ;p)

I purchased a brand new 2012 kia optima. And was very hesitant into putting a system in my car because from past experiences I have had exceptional sound but my alternator and battery always seemed to die over time. So I decided to go with a guy that many people have referred me to who used to work for west coast customs. He explained to me the reasons my past systems might have been having those issues pertaining to not having the right type of amps, cables, fuses etc. He does make a lot of sense with what he said. Well I decided to buy some JBL component speakers that I had in previous car that sounded awesome! Almost like i had surround sound in my car. I gave him the speakers to install into my factory stereo at the time. He encouraged me to get an after market stereo because im not going to get the proper sound that I was looking for with just the stock stereo. I refused at first and just stuck with it. the kia optima stock normally has a 6 speaker system. (2 back, 2 front, 2 small speakers by the windshield) what he did was custom make me some holes in my front and back door panels to fit the tweeters and added another pair of tweeters by the windshield.

When he had everything hooked up it did sound better but i could see what he meant by not being clear. He suggested an amp to enhance the sound which i did and that helped as well but the highs would also be distorted. I noticed that he did not put the crossovers in the car with the speakers. when i questioned him about it his answer was directly this " Crossovers take power away from the speaker and it doesnt make a difference to the sound quality. Its like filtering out sound and you wont get the full range of the speaker" That made sense to what he said but no sense to what I read over the internet. Crossovers are supposed to distribute the sound of different frequencys for instance only highs to the tweeters and only mids to the mid range speaker etc. When i printed out paperwork to show him he continued to refuse to put them in saying it would be stupid to put them in that car audio companies only put those in to save the speakers to last longer yet they are only half as good sounding like that. Still didnt make as much sense but i gave him the benefited of the doubt as I hard already learned alot from him to prior conversations.
Anyways He also installed a Alpine PDX-F4 digital amp. Which he claims is better than the other larger JBL amps i used to have because those drain my battery. So I decided to go with it. He was correct I haven't had any issues with my battery or anything like that. We then installed a PDX-F6 with two 12 inch kickers which sounded very good for subs but the highs were just terrible. He said if I got a after market head unit that it would eliminate that problem.

Fast Forward...
After I saved up some more money I had him redo my entire interior (new seats, lights, headliner everything came out great!!!) I also purchased the Pioneer x930bt navigation head unit... (his reccemendation) as well as new tweeters since the ones I had were previously blown. He suggested to get coil tweeters because they were cheap and sounded great. I said ok. He hooked everything up including a module for my steering wheel for all the controls to work, took out the eq since he said i wouldn't need it anymore. And there was a huge difference!!!!!! But.... The highs still seemed to be a bit to high even at a somewhat of a low volume and the last 3 bands at a flat or -1 eq.. You would still here too much chhh chhh sounds. I started to think it was the cheap tweeters that he suggested. After 1 month I needed to go back since the tweeters were blown again! I kept trying to get an answer on why this is starting to happen. He said tweeters always get blown out but your under warranty so ill just hook u up with some better coil tweeters at no charge. With the new tweeters. Those lasted about two months. Keep in mind i never blast my radio over the threshold probably at 70 %or 75% are set on the gains for the amps, so i knew something else was wrong.

After about 4 months of just dealing with it. I started to notice that i wasnt getting all of my sound for certain songs, like different notes were missing and i had to turn my speakers up even louder to get the same volume level. I figured that my speakers were blown or the tweeters again! I went back and he said that 2 of the speakers were blown and the tweeters were also out. He said i should have gotten a different type of speakers. since components are only the tweeter and the mid-range where as a 3way,4way or 5way would have all range of sounds and sound alot better (at this point i was definitely questioning he expertise) I have always been told that component speakers were the best and the same exact component speakers i had in my previous vehicle sounded amazing where as these sounded like there was way too many highs. It just didn't add up. He said to trust him and go with some 5 way pioneer speakers that he would hook me up with some more tweeters for free. Since all 6 tweeters were blown he said maybe there is too much highs also because you have too many tweeters so we will just put 4 in to lower the highs. about 4 months ago he changed everything out. For about 2-3 weeks everything sounded great and now back to the same issue. An extreme amount of highs that is now unbearable to turn it up and some mid range frequencies are also sounding very weak and distorted.

If you had the time to read everything, you can see my frustration! if someone could Please let me know what I should do and explain this to me in detail I would love to understand the way car audio works more so then just getting it fixed right. I have had four systems in 4 different vehicles. This has been the most expensive one and seems that no matter what i do the sound still sounds like ***. The lows and subs are great i have no issue with those but everything else is just not up to par at all. Do i need a crossover? do i need to get really good tweeters? go back to component speakers? was 6 tweeters a good idea?

Any help would be greatly appreciated. Thank you.