I haven't heard the VSD3 yet (actually, no one has since we only have the VSD3S). I can tell you the VSD1 and 1S have much more bass than the VC02. The VSD1 has more midbass and is boomier, while the VSD1S has a bit deeper bass, which is tighter. The bass is not all that different but it is noticeable. I don't know if either is as clear as the VC02, as I don't know it personally, but if you're looking to upgrade, especially in the bass department, the VSD1 and 1S are good options.
The VSD3S should have bigger bass than the VC02 and people in this thread have pretty much unanimously said it's better than the VSD1 series. I can't recommend them personally as I haven't heard them yet, but Peter123 and Kova4a are both in agreement that it's the superior of the two. My ears tend to trust what they say, so I'd say the VSD3(S) is the way to go.
Hope that helps out a little.
Well, vsd1 and vsd3 are very different from the vc02 in the bass department. They both have bigger and fuller bass while the vc02 has a pretty flat bass, which is tighter and has great punch. As some people around here know I never was a huge fan of the vc02 - I liked its bass and think that overall it'a pretty clear and balanced iem but I found its treble splashy and kinda artificial sounding and soundstage-wise it's very two-dimensional and really lacking in depth.
Guys, it's awesome how friendly and helpful one can be ! Thank you all so much... I wish I also could be of this much assistance !