Fastest subwoofer?

It's hard to go wrong with REL.

+3 or+4 for Vandy 2Wq......2 of them of course :^)
I've had REL Stadium II and there is no real comparison.
Fast, clean, deep and most importantly.......leaves the signal to the main speakers absolutely pure and untouched.

I have owned the Vandersteen subwoofer and it is very good. I like how it connects to the system relieving the amp and main speakers of the lowest frequencies. However, I feel the REL is better and is much simpler to connect and dial in to the system. The REL does not sound like a subwoofer it makes bass music.

I am currently using a REL T5 with my SF Guarneri Homage speakers. The GH's are lightning fast, the REL is a very good match, if that says something about their speed. Depending on room size, I would highly recommend the T5 if one is using a small to small/medium size room.

Over time I have had B&W 6,Rel Stadium III, Aereal SW12 & now JL Audio F113. The JL's are the fastest out of all of them. The only issue with the JL's is there is no LFE input so if you want to use them with both HT and 2 channel they are harder to integrate. I ended up using the NHT X2 crossover.