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.
CDT carbon fiber 6.5" mids & DD T2 tweeters on a Polk Audio PA D4000.4
Tantric HDD12 in 3 cubes/6x17" aero on a DC 5.0k
2 runs Monster Cable 1/0, SounDrive rca's, Singer 310a 6 phase, Exide G78 agm's, plenty of deadener