I think you'll have to luck upon someone who actually owns both cameras for a definitive answer - but I can make a pretty good guess.
Your considering a model that costs half what the VX-2100 costs, a model that does poorly in low light especially compared to your VX-2000.
But they're both Sony's, so presumably the color temps will be close. In good light, you'll probably be OK. In low light - forget it.
Sure the PC1000 is smaller and lighter, but what is quality worth? My advice would be start going to the gym, at least until the weight of the VX2000 doesn't bother you anymore. :)
PS - they don't make the 2100 any longer, so don't wait until 2007, they'll probably be gone from the shelves by then. But then, so might all the other SD cams - have you heard HD is coming?