If you decide to buy another Mac, check out Apple.com and on the Shop page look at the refurbished mac section. I've bought several and saved quite a few dollars ... they also come with a great warranty. I typically buy low-end, then add my own memory and upgrade to a larger drive vs paying Apple $200+ vs $75 to get the same amount of memory from say crucial.com.
Also, if you do buy another Mac, make sure you check the model # and specs to ensure it will run OS/X Mountain Lion. Older 2007's, etc won't run it and you'll be left with Snow Leopard (a main reason you see a lot of macs for sale on e-bay, they can't run Mountain Lion).