Yes, go with the 880PRS HU and run those Type X's active.
Here's my recommendation for your budget range:
HU: 880PRS $275-330
Front Comps: SPX $145 (yes, get them!)
Front Amp: JBL GTO75.4II $220
Sub: Fi Q15 Dual 1 Ohm VC $280
Sub Amp: JBL GTO1201.1II $300
Sub Box: $25 sheet of 3/4" MDF
Don't forget to factor in costs for wiring, souned deadening, install accessories, etc.
These prices are all approximations, so some power shopping might yield lower prices.
You might be able to get a little return on the Sony HU here, on
eBay, or from someone you know that needs one.
If you want to save a bit of money on the amps, check out the Power Acoustik SL lineup.
SonicElectronix has the SL4-1000 for $115 right now.