Good Bass Floorstander under 1K

NHT is affordable, especially used, and known for having an extended low-end. I owned the 2.9's for a while and can attest to the reputation. Some models have styling that is not for everybody. In any case, the VT-2's are an older speaker, often available for below $1K used, and fit the bill. The 2.4's may or may not come in below a grand, but would fit the bill as well.

The PSB Gold i at $900 seems like a no-brainer too.

find a pair of castles.

Second Ghunter & Kthomas. Large bookshelf speakers in your price range will give you better sound quality. NHT SB3 responds to 39Hz and placed properly will convince you of it.

Old NHT 2.5i's are in your price range and will give you lottsa-bass. Also Kef has the Q5 that technically doesn't respond all that low but is ported. It is a good reasonably priced speaker if you want some bass + a sexy cabinet.

Good luck!

used vandersteen 2ce's....

Well a used pair of SOliloquy 5.3is is a great suggestion. But good luck on finding a decent used pair. The wanteds listing on these gets longer as the supply of used gets shorter. Totem Rainmakers are good. I actually have a pair of PSB alphas that have suprisingly good bass extension, so perhaps that line is worth a looksee aswell. Ascend CBM 340s arent bad but I wouldnt quite call them floorstanders although they are much taller than your usual bookshelf. I cannot recommend the Rocket 550s to you. How bout the Energy Veritas Line used or perhaps Quad 12Ls? These last two I HAVE NOT listened to but have read about in detail and might be worht your time to audition. These are audtion recommendations, not buy recommendations. Also, I think a used pair of USher 6311s might be worth your time if you can find them at your price point used.