does anyone know of a scoket 478 motherboard that supports pcie?

They exist but are hard to find.
http://www.albatron.com.tw/english/it/mb/specification.asp?pro_id=147

do you know if this is a pretty good board? would it be worth the switch just to put a better graphics card in it?

It's probably ok, but if you already have agp 8x you can still get a pretty good card installed, like a 7800gs.
http://www.newegg.com/Product/Product.asp?Item=N82E16814130275
Or if you don't want to spend that much a 6800gs would be nice for $225usd
http://www.newegg.com/Product/Product.asp?Item=N82E16814143045

If your sig is correct, then you have an abit IC7 which is a nice board. I don't think you'll see much advantage to going with pci-express unless you want a top of the line $500-600 card that isn't available in agp.

yeh ive been lookin at that one but now that the 7900 series came out i think im gonna try to go for one of those, but dont want to pay another 300$ for a cpu and 150 for a mobo..so im tryin to just find a 478 pcie mobo