I know you guys will probably hate to hear it, but how about the Kenwood small box 10"? I have 2 of them, and each is in a .88 cu ft sealed box and they sound great. I am running about 120W RMS to each sub. They are only 4 1/2" deep and cost about $59 each (Buy one get one sometimes for $100). They barely ever "bottom out" or distort, but if you are using anything other than a sealed box they probably will not work for your application(based on the size of box you are wanting to use). BTW, I think they are more toward a SQ sub than an SPL if it matters. I have the blue ones, but the new silver ones are the same specs, just different color cone. If you need any specific specs, I have the booklet right here.
Edit:
Kenwood 10" at Crutchfield
