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.
Source: Pioneer DEH-80PRS
Front stage: PHD FB6.1 Pro & Vifa XT25BG60-04 on a Kenwood XR-4S
Sub stage: 2 Tantric HD12's on an Autotek MM 4000.1d
Electrical: 310 amp (lol...) Singer Alternator, 2 Wėrker 125ah batteries in back, +/- runs in Monster Cable 1/0