Only having experience with the F12, and only reading up on the v1220, HSU STF-2, and DWS 660, I'd go with the HSU STF-2.
Simply because I hear it's a good quality sub at a reasonable price. The F12, while good for the price, simply leaves you wanting more after a while. I'd recommend it to anyone looking to spend under $200 or so, but if someone has the ability to buy the STF-2, then I would suggest giving it a shot.
But, you could add the Klipsch RW-12d to your list. Currently at $350 on newegg, and regularly getting down to $299, it's a great sub for the money.