I'm intrigued by the two versions of the B3. Is the Pro version more expensive? Right now I don't think I have the funds to go with the purchase, but if it had a similar look to the IE80 (refined, formal look) then I'd take it. The B3's housing looks like it's trying to make a fashion statement (black/red reminds me of B****). I'd like something more understated, because judging from the pictures, I'm willing to assume that it might be more of a head-turner than anticipated.
I'm also quite perplexed with "everything else being near-perfect" as you say. I'm a basshead, so I really would like more bass. However, I crave a lot of sub-bass (like what the LCD-2 offers), so if the B3s do well in that respect, I might actually want to buy it. I'd also like really great positional accuracy, as well as great mids. I do not like sharp treble, so if it's pretty sibilant, then I should probably stay away.
Also, there's one more thing. You said that you could "guarantee" that it will sound better than the Pistons. Does that mean you don't own the Pistons? And don't the Gratitudes (which you said was your other favorite) have a fun signature?