After spending a few years playing with car audio and headphone setups, I decided to spend a bit of time on something different and build a decent stereo/HT setup. I've already picked up the receiver and speakers - a Marantz 5006 and Arx A5s - but I haven't decided on a sub yet.
Couple caveats - I'm doing a 2.1 setup rather than a 5.1 due to room size; I'll primarily be using this for music rather than HT (I'd say about 70/30 split for music to HT);and I want as musical and accurate a sub as possible - if that means losing some uber-low frequency and window-rattling abilities, well, everything's got a trade-off. I listen to everything from Amon Amarth to Dead Can Dance, and Agua de Annique to Arch Enemy.
I've been looking pretty hard at the PB1000 and the XZT 99.W12.16, as both get pretty good reviews when it comes to accuracy and music. The VTF2 MK4 is on the list too, but seems more biased towards HT duties.
Budget is about $650 or so - that's pretty much the maximum, since I'm spending a bit more than planned on the speakers and receiver.