What i'd do personally is, find the cheapest retailer that sell these new and then see what the final price is likely to be near the end of the auction. If the auction price is close to the new retail price i'd buy it brand new because that way you get a warranty and satisfaction that if something goes wrong you can send it back. However, if it seems to be going extremely cheap compared to its retail price then if something does go wrong you don't loose much money.
When I bought my G25, people were selling used ones on ebay for about 50UKP cheaper than retail (approx 100USD cheaper). I bought mine new because I beleive paying that extra 50UKP for something that has warranty is worth it.
So unless it goes for an extremely silly bargain price, it may be worth buying one new, so that way if it brakes after a month of use you can send it back and get a replacement.
Anyway, like I said, these are just my beliefs, and I have a fairly strict buying strategy anyway (i'm tight with my money - I get moths flying out my wallet when it gets opened).
ok thakns ill just go to best buy and get a logitech momo wheel since its cheaper than the g25 so i can buy s2 also then later on ill get the g25 for christmas