spl=Sound Pressure Level
SPL comps are also called Decibel drags. Count on spending much more than 4k to compete with the big dogs.
If you want to have a chance at being competitive, go for Sound quality (SQ).
That being said, if your goal is to get as much bass as you can from your system, I would go with the following setup.
Head Unit (HU): Get a HU with at least 4V outputs. ($300.00-400.00)
Amp: Get one of the many Class D sub amplifiers from companies like JBL, MTX, MMATS, or Orion. They all seem to have 1 ohm stable sub amps that put out 1000-1200 watts. (~$500.00)
Amp for front speakers: Look for a high quality 50 watt per channel 4 channel amp. PPI, a/d/s/, Phoneix gold would be good choices. There are many other good values.
Subwoofers: There is a huge variety of subs that would work well. Here are a few to consider. Avatar Audio Tempest (15") for about 140.00. Comparable in output to most $300.00 subs with better SQ. Eclipse aluminum cone woofers, Audiobahn, Adiomobile, Digital Designs, Ground Zero, and Volcano subs to name a few will all work well and will cost 150-400.00 a piece.
Installation: including cap, wires, dynamat, etc...Don't skimp here. Buy 1/0 Guage wire, a 2 farad cap, LOTS of dynamat. Spend about 400.00 on sound deadening to start. You can get good prices on sound deadening at
www.partsexpress.com and
www.mcmaster.com. Also, don't skimp on RCA jacks. Get fully shielded wire from Lightning, Streetwires, or monster cable.
Mids/Tweets: Look for 6.5" components for you front doors. Check
www.zalytron.com for good deals on Focal components sets (350.00) and
www.madisound.com, on the on-sale page, for the Vifa component sets. Also, check ubid periodically for deals on RF fanatic components, PPI seperates and other brands. You can get good deals. (250.00-550.00 for both front and rear)
FOR SQ:
a/d/s/, McIntosh, or Xtant amps. Phoenix Gold is another good option.
Stick with focal, a/d/s/, diamond hex, or dynaudio component sets. (expect to spend about 300-700 on the front set. You can go with only a mid for the rear speakers. you won'd need a tweeter for rear fill.
HU: Go with a high end unit from Eclipse, Clarion, Nak, Alpine, Pioneer (DEX-P1R) or the Sony CDX-C90 (IMO, the best HU made). McIntosh has an extremely good HU but it wouldn't look good in our cars.
I'm probably forgetting something...
dave