looking for cheap subs with a good sound

Hey everyone i have finally made my decision. It was a long fought battle between Powerbass, lanzar, SPL, Lanzar, planet audio, hifonics, and some other low cost companies but with the Airspace, mounting depth, QTC, and rms wattage. I came out with...

The Powerbass M-10, M-series :

• Power Handling Capacity (Peak) : 600W

Enclosure Specs:

I chose this subwoofer because-

• The 300 RMS wattage of the subs for my 1300wrms T10001bd amplifier is perfect for 4 of these. Because I am able to get the subs full SPL capabilities without maxing out my amplifier. (in a sealed enclosure, I know ported would be much better)
• The QTC suggest that this sub is capable of playing nice low notes in a sealed enclosure
• My enclosure is going to be about 2.75 cbft so the minimum .5cbft is perfect.
• the mounting depth is good for a easy enclosure build under my back seat of my truck. ( rear seat lift)

I will be starting out with 2 of these subs. And if I am impressed I will buy 2 more and build the four 10inch enclosure

If im not impress then Lanzar and pioneer will definately be in the running

Thanks for everyones suggestions.

Yeah change of plans im gonna go with the 4 Pioneer TS-W258D2. Ive been doing even more extensive research and these just came out and with a beatiful frequency range of 20-180hz. ( I listen to alot of bass dropping songs) hopefully this means that it is specializing in this low range very well and Alot of people like the first model. i think this is one of those subs you can just kind of trust... if that makes sense. 

Do you think it would be a problem to possibly under power them 20-50 watts? well not really a problem but just noticable?

I second that because I use to work in a car stereo shop and when a customer installed some Lanzar subs it would almost certain they would be back with some wierd problem like the cone seperating from the spider or the flexible wire that goes into the sub from the terminals breaking off, etc. I dunno how long way they have come now...

Speaking of cheap subs that sound good, I bought a set of 15" Ultimate dual 2 ohm (yeah ULTIMATE wow) off Ebay from some teenager who never got to use it. Long story short, I wish I could find more of these because these things sound GREAT. I have looked high and low but never found any info on these. I try not to put too much power into them though - the SQ is amazing for it being Ultimate not to mention they sound loud too.

Yeah I was looking and the CHAMPION series 10inch I can find for like 60 bucks! then I was looking Both the Pioneer and Pioneer Premiere have came out with a new Champion model subwoofer. (The premiere about 10-20$ more) I was trying to see what the difference was between the subs and all im seeing is

the spider on the Pioneer Premier (TS-W1008D2|D4)  is "Aramid Fiber" and the Spider on the Normal Pioneer model ( TS-W258D2|D4) it is "Conex"

Is it really worth paying more? Does the Aramid Fiber allow more excursion or is more durable?

and the only difference between the Old (TS-W1007D2|D4 ) and the new TS-W1008D2|D4 Champion series is the Gasket is now "ABS" not "Molded"

What is the Gasket? Is this going to increase anything or make the sub more efficient?

Thanks Again. And Also I am buying 4 of them.