The w6V2 is a very good sounding speaker.
The Type X is overpriced and inefficient IMO but still a good sounding driver (not in the same league as the w6V2 and the other two I am about to list but still good).
OZ Matrix Elite and Image Dynamics IDMax are in the same league as the w6V2 in SQ but easily beat it in output. Something to consider as you stated you want a sub that will "bump". 600rms is plenty with either of these two subs also. Price should be comparable if not cheaper than the two you were looking at.

Alpine makes decent amps. You might consider going with a bit more power instead of the 345 especially since you stated you like your music nice and loud. The added headroom of a larger amp may be of benefit to you. A good set of components will like some power on tap and not a tapped out amp.
Lots of other amp choices out there that are just as good sounding and reliable as the Alpine that have more power for the same if not less dollars. JBL for instance can be had for excellent prices especially online.

Don't worry about adding a stiffening cap at this point.

Whether you want to run rear speakers in your car is personal preference. Many of us only use speakers up front and skip the rear fill opting for the best speakers we can afford that ours ears feel are best up front provided with penty of power.

As for crossovers most amps these days have more than enough to take care of what you're planning in this system.

 

Thanks for the responses, much appreciation...If i'm running 2 amps (mono block & 4 channel), let's say for now the 2 alpines I mentioned, shouldn't I have a power cap? If not, when would such a cap be appropriate? Is the 14.4 voltage an advantage when picking an amp?

Also, I quite liked the JL components when I heard them a couple years back...Anyone have some thoughts on the newer versions?

 

If you're at all on a budget money is better spent in other areas. For now use some of that money to maximize the potential of the factory charging system by doing a "Big 3" upgrade. Do a search here if you are unfamiliar with what that refers to.

Money saved by a cap at this point could also go towards speakers your ears love but are otherwise out of your price point or for more power to run your speakers to their full potential.

Although a cap does have its usage in car audio all of these areas take precedance over it when putting a system together.

Don't limit yourself to the JL drivers just because you liked them years ago. Go out and listen to lots and lots of the great choices that are available today and then buy as much power to run them as they require to really shine.