You can get an x38 board for around $220. 8800GT, New8800GTS, and the HD38** are PCI-E 2.0 cards so unless you don't have one of those, then I wouldn't bother upgrading to PCI-E 2.0 yet.
Also since the 680i chipset doesn't support 45nm CPU's and the 780i is the 680i with a PCI-E 2.0 bridge chip, I wouldn't really put my money on it being all that great. Plus from what I've heard the 780i doesn't have the full ability of PCI-E 2.0 because of the connection speeds between the bridge chip and the NB.
Overall I'd just say wait till the end of February. If you "neeeed" a board right now and want PCI-E 2.0 I'd get an x38.