whats up

right now i am diving an e36 bimmer and have a few things done to the system. i completely gutted the crappy stock system and currently run 5.25" Alpine Type R's all way round powered by a 4ch Kaption amp. my weak spot is definetly the coaxials in the rear (components are in the front) and i am going to get rid of them. no question about it im throwing in some Boston pros.

my problem lies in what sounds better. what is the difference between 5.25" and 6.5". most stores only have 6.5 on demo. Do 6.5" pros sound better? i find my current system lacks good mid-bass.

My other problem is what to power the pros with. My kaption is rated at 50 watts x4 , but i think it throws out closer to 100. This is under powering the pros but will it sound better than what i had?

Eventually i will throw another amp in and i hear the BA pros really scream with 200 watts rms pumped into them. Do they really handle that much?