I'd probably go with eBay. As long as you check up on who you're dealing with and use PayPal for your purchase, you can get some decent stuff at a good price. You might want to get one of those 'ebay for dummies' books first though. There's definite insider tricks to 'power bidding' and looking out for stuff like hidden shipping charges, best times of the day to bid, watching items and how to outwit 'snipers' etc...
Just get everything in writing and use PayPal so you have some insurance if you get shafted.