Hi folks. Liking to buy a 6 month old current model 21.5 " iMac with an i5 and 500 gb Hard Drive. I have someone who is willing to sell with box and receipt from Best Buy for $900. Is this a good deal? I will be in need of a new iMac within the next 2-3 weeks, so I know waiting on the new models will not benefit me. Any input I appreciated.