Saw eVGA were flogging 4xx series cards reconditioned before christmas. Seen some 580 cards around more recently too.
Think the guarantee is for like 3 months, but I did notice the seller also had in their defined warranty description for 1 year (which I quickly took a save of the webpage for legal reasons).
Around £160 for both a 480 and a 470, to go in a game rig and a cuda transcoding rig is pretty good imo. Seeing as the 480 broke all the records in it's time, despite being trashed by overclocker-heathens, I did turn to Icy.. Cool.. something, 3rd party coolers and clocked the crap out of them. (well the 470 has it coming).
If you aint getting them dirt cheap, and have a plan in mind, buying them in this day'n'age is... well, silly really. We'll almost be talking 3 generations old and the newest drivers aren't the best to use on them.
Is pretty shocking tho that 3rd generation tech still kicks a games butt. Don't be worrying about the vRam, your 2000+ jiggahurtz ddr3 main memory will cope with any overspill at a minimal reduction in potential fps.