Something really cheap to keep a look-out for is a pair of Zenith Allegro (2000 or 3000, can't remember which) speakers. They pop up at thrift stores and garage sales a lot. Be sure it says 16 ohms on the back (8 ohm ones are ceramic magnets). They have a 10" woofer with an impressive AlNiCo magnet on them. Cloth accordian surround. Qts is a bit lower than what you're looking for (around 0.35), but they have a lot of punch. Fs is around 32Hz. They come in a rather crappy built BR box made of partical board with about a 2500 Hz crossover and small horn tweeters. I put them in a TQWP and had very impressive bass right down to 30Hz. Taunt and clean. I think they have a 1 1/2 inch voice coil and can take a pounding. My son used these from when he was about 14 years old until he was in his early 20's and gave them hell regularly with a Marantz 2275 cranked into distortion. Fried the tweeters, but the woofers survived to later be used in my TQWP's. I've seen these go for under $20 a pair.