Amp selection for porsche 996
 

I am planning to upgrade my factory stereo, I have a 2004 Porsche 911 carrerra 4S convertible. I already purchased:
- 2 sets of Polk Audio SR5250 Component speakers for the front & rear
- 1 set of Polk Audio SR6500 Component speakers for the doors
- 1 pair of 10" Digital Designs 2510 subwoofers
- 1 pair of 10" JL Audio 10W7 subwoofers
I will only use one pair of subwoofers, but have not decided on the one.
Subwoofers will we installed in the rear footwells.
I will use Pioneer AVIC-X920BT as Head Unit

I am having a hard time selecting an amp to run my set up, please help by making suggestions.
I considered the Cadence ZRS-C8 because it's a 5 channel with lots of power and I wouldn't have to run 2 amps, and it only cost $449, I also considered 1 Alpine 4.150 + 1 Alpine 2.150 for the components and getting either a JL or DD amp for the subs.
I'll be buying the amps used and would like to spend around $500

Please advise
Thx