
Maybe I am missing something here, but you have 3 sets of speakers listed, thats 6 speakers by my count, and you are getting a 4 channel amp? Are you planning on letting the head unit power the dash speakers? If so, there are a few things you should know. If you are just looking for volume, then you can probably wire the dash speakers to the head unit, and the 4 channel to the other 4 speakers, but if you want it to sound nice, you shouldnt do that. In my experience, I have found that when you hook 1 set of speakers to the head unit, and the other set to an amp, you have a tendency to get a little bit of an echo because they are not all making the same noise at the same time. It may not even be that noticeable, but then again depending on the quality of the wiring to the amp, it could be very noticeable.
If I were you, I would change things up a bit with your system... I always recommend Infinity speakers, not only are they REALLY loud, but the sound quality at all volume is the best. They are the only speakers I mess with...Now they have two "series" The Reference series, and the Kappa series, the Kappa series, which is more expensive ...
http://www.etronics.com/product.asp?stk_code=inf6525i&store=&catid=358
And the reference series...
http://www.etronics.com/product.asp?stk_code=inf6802cf&store=&catid=359
NOTE: I DONT APPROVE OF SHOPPING AT ETRONICS!!!! The only reason I gave you those links is so you can see how cheap they are there. Now you can get the speakers for 5% cheaper than that! Go to sounddomain.com and fill out one of their 105% price match things, with both sets of speakers. Then you will be getting both sets of those speakers for only ...
$60.00+$90.00=$150 (then take 5% off) Total= $142.50 Those are REALLY nice speakers (even if one set is reference series) they will be much nicer than Sony and Pioneer sets.
Honestly, I would skip the dash speakers, worry about them later, just pull the current ones, and have 2 sets total. That way, you can keep the same amp you wanted the Alpine one, but check etronics and sounddomain for the price of your amp first because they will probably have it $20-$50 cheaper.
I have nothing against crutchfield, they are GREAT, great customer service, free shipping, fast shipping, and great return policy. I have bought so much from crutchfield (over $2000) in the last 2 years, they signed me up for a free subscription to Mobile Entertainment Magazine for 3 years!!! They are awesome, HOWEVER, if you are pinching pennies, and need the most bang for your buck, do what I mentioned above with the 105% pricematch. Let me know if you need any more help...