Re: decent speaker for a garbage ride...
Front: (use mdf or a cheap adapter to fit)
WoofersEtc.com - CL-S50A - CDT Audio Classic 5.25" 2 Way Component Speakers
edit: Forgot that 6.5's will work with an adapter, too... so these would be better if they can fit in the budget.
Rear: WoofersEtc.com - SE8375 - Eclipse 5 x 7" 3 Way Coaxial Speakers
Run the CDT's off the amp and the Eclipse's off the hu. Use the remainder of budget on a couple of sheets of Audiotechnix 60 mil deadener.
Rockford Fosgate t800.4, CDT ES-MO 6 mids, Digital Designs T2 tweets
2 MB Quart DSC1500.1's strapped on 1 Tantric HDD 12
Mike Singer 310 amp 6 phase
2 runs of Monster Cable 1/0