Newbie question on amp power and choice

I am looking for some advice on choice and power of amplifiers for the following set up for an aftermarket install in a Volvo V70R.

Alpine IVA-D300 - Dynaudio System 360 3 way set up (8"/3"/1") for the front speakers and will either leave the stock Volvo speakers in the back (6.5" / 1") or replace them with some cheaper but better alternative. I will add a new center speaker 5 or 6.5" component piece. The stock amplifier was a Volvo amp rated at 75wx4@4. I plan on adding a PXA-H701 5.1 processor at a later date, but not initially. (I am running an Alpine CD Changer, XM Radio and iPOd interface thru Ainet connections)

On the SubWoofer side, I have limited space and am leaning towards one or two small 6" or 8" SWs from JL Audio, but am open to suggestions and advice. Space in the trunk precludes anything over 8".  I plan on building a custom box that will fit behind the rear seat but in front of the small 3rd seat (remember its a wagon !)

In researching the power requirements, I have come up with the following:

The Dynaudio set up will handle upto 200w@4ohms, but work well at anything over 100w;  the rears are really only filling, so anything over 75w for them and the centers is really overkill.  The subwoofers appear to need between 200w and 300w.

The challenge for me is what amplifier combination do I use to satisfy this need?  I think that I am going to need two amplifiers and had considered using one to drive the front and sw and one to drive the rears and center.  Another thought had come up - what about using the head unit to drive the rears and center by taking the rear speaker feed to the rears and combining the front speaker feed to the center speaker (the D300 is rated at 18wx4RMS).  But I am not sure if this would work?

Suggestions and advice is welcome, the options and choices found researching this forum are mind boggling (:

Thanks

Nick

You wanna know what I'd do if I were at all interested in eventually going multi-channel? 

I'd get these:  http://www.xtant.com/html/products/xtant1.1i.cfm

One for each channel you are running.  They are tiny 6.5" x 5.8"x1.63" (i.e. can easily fit under seats or tucked elsewhere), they are very efficient (class d), they are full range, they produce excellent quality sound, and they are quite powerful. 

Initially you could go for 2 or 3 (if you do the center right away) and power the rears off the deck until you buy that processor and / or buy the center. 

Then get a regular subwoofer amplifier for whatever subs you pick.  http://www.xtant.com/html/products/xtant3.1.cfm  would work well.

I like this solution MUCH better than an all-in-one solution.  It is much more flexible than any other solution and the price per watt, considering the sound quality, will beat almost anything else I can think of.

What do you think?

Interesting proposition, I will look at these xtant products.

Another thought came to mind to support flexibility:

Run a multichannel amp for the front and subs - I looked at the Alpine MRA-F450 120wx2@4ohms & 200wx1@4ohms) or the MemphisBelle 16-MCD600 ( 125wx2@4ohms & 400wx1@4ohms) and I think JL has a similar product;

And then get a mono Class D sub amp and run the two rear speakers and the center speaker in series mono not stereo, the speakers are all 4ohm and around 50-75w RMS rated.  This would be driven by the headunit rear pre-amp output?  I think something rated at 300-400w@2ohm would be OK, or have I messed up my math again..

Is this crazy,

Thanks