And I thought you were Mr. Factoid machine...
To the OP, heres a great shallow mount: Parts-Express.com:Tang Band WT-1427G 10" Neo Subwoofer | WT-1427G subwoofer 10" subwoofer low profile thin mount neodynium subwoofer tangband tb speakers
Heres another good one: Parts-Express.comayton QT255-4 10" Quatro Subwoofer 4 Ohm | subwoofer qt255-4 10" subwoofer dayton quattro dayton subwoofer dayton 10" woofer email-quatro-4-3-08 DayAudSub11408
Parts-Express.comayton RSS265HO-4 10" Reference HO Subwoofer 4 Ohm | subwoofer rss265h0-4 10" subwoofer dayton reference rs sub dayton loudspeaker reference-22008
That last one would be the best in your price range of ~$100
Things you should care about: Xmax, sensitivity, power handling. Everything else is irrelevant in your price bracket unless you want to go ported or sealed.