I've heard quite a few 8" subs including the RE8, the TangBand W8-740c, Stereo Integrity's new 8" sub with XBL^2, the JL Audio 8W7, and maybe a few others from back in the day, but these are the most recent ones I've heard. So I can't really comment on the 8W3v2. Here is how I'd rank these subs in performance.
8W7 is hands down the best 8" sub I've ever heard, period. In fact it is my favorite sub out there right now, and I've owned some great subs (Brahma 12, Magnum 12, E12A) and had alot of listening experience with a few other very nice subs as well (XXX 15, IDMAX 12). I love this sub. It's not practical by any means though. It costs way too much money and it needs a box twice the size other 8s need. Those things aside, its flawless.
Stereo Integrity's 8" is next, flooring the RE8 and TB8 by a good margin. It's got plenty of low end and tonally it's an amazing sub. Priced a bit higher than the RE8 and TB8 (roughly $100 versus roughly $50), its a better sub all around. Considering that you could have three of these for the price of a single 8W7, its also the 8 with the highest value IMO. Stereo Integrity is planning on releasing this sub very soon, and I think people will be very pleased with it once it hits the market.
The RE8 and the TB8 tie for third place. Both have their ups and downs. The RE8 lacks on the very bottom end and its easy to bottom out the former on the backplate trying to get it to hit those lower notes. Besides the lack of low end (which can be overcome with more cone area, and a pair of RE8s do just fine down low, but a single RE8 has some trouble) the RE8 is a very tonally smooth driver thats just a nice little sub all around. The TB8 doesn't have the problems with bottoming out like the RE8 does, but it needs more power to get going (and doesn't have much more output than the RE8) and it isn't as smooth tonally as the RE8 is. If you're using a single sub, the TB8 is a better option IMO, but if you want to throw a few 8s in the RE8 becomes the better choice IMO.