Just had a quick squint at the recommended spec for WoW - they reckon a NVIDIA GeForce 8800 GT is the ideal card. Wikipedia informs me that the 8 series came out in 2006!
Even an Intel HD 4000 seems to manage almost
40fps at 1600 x 900.
Deanna - If you're happy with the way your current setup plays it, I reckon pretty much any new computer will be adequate for WoW. Alternatively, something like
this would meet the WoW requirements (and is on the supported cards list). That would keep you going till you're ready for a more major upgrade. Of course you'll need to check that it'll work OK with your PC - I have no idea what power requirements it has, or what power and interface connections you have available etc.