Hey there...
When I bought my Studio .v4 setup, I was able to audition the .v3 and .v4 side by side...
Honestly, there was barely a difference in the sonic signature between the 2.
I liked both, and couldn't tell much of a difference between them, the mid's on the .v3 were a tiny bit thinner, but not enough to equate to a large enough difference here.....
The only upgrade with the .v4's was the mid driver and the dome on the .v4's was changed to gold, but you didn't get the whole tweeter handed down from the signature line, just the dome or cover... so it wasn't a huge step up from the .v3 to .v4, I just wanted the new hotness when I bought my first set of quality speakers....
Personally I don't think you can go wrong with a set of .v3's..... If your getting a good price hit it.... Check what the dealer is giving you on a price on the stands.... You can usually get a really good deal on Audiogon.com for stands, I got them for a fantastic price there for my Signature S4's (same as the Studio 40's), and they are great stands, very well built...
Good luck with your endeavor...