The V2 started production 2002. They are generally regarded as excellent SQ subs. Low xmax (comparatively), low moving mass, very high sensitivity. You could make an IDQ10 sing with 50W of power. Very musical, very detailed.What's the difference between a v2 and a v3?
The V3 started several years later (I don't know the exact date), but they have higher power handling, higher xmax, but still retained some of that sound quality. They still have a very low moving mass, but can dig deeper. Some say the IDQ V3 sounds just like the IDQ V2 but with a higher power handling. I suppose it depends on the kind of music you listen to. The IDQ V2 drivers aren't drivers to be used for rap, hip-hop, dubstep, or any synthetic bass that digs below ~40hz. It will play those notes without a problem, but the limited mechanical excursion will have them bottom out more easily. What I'm trying to say is that if you want an SPL driver, the IDQ V2 isn't your cup of tea unless you use them in multiples or get the 15" like the one I have.
The V3s will sound similar, but will require slightly larger boxes, have higher power handling, and have higher output capability.
I guess to summarize, the V3 has higher output, but the V2 has slightly better sound quality. I'm saying this compared to each other. The V3 IDQ is still significantly better than just about any other sub in its price range in sound quality, and both the V2 and V3 are pretty close in sound quality. The V3 of course is going to be more expensive.
If you buy an IDQ V3, you will certainly not be disappointed.