A Mac store is selling this model iMac (MA878LL/A) with a sale for the tax free holiday here in Tennessee. That model is not the current one.. and is there any major difference I should be aware of between the two? I was originally going to buy this 20" iMac (MB323LL/A), but with this sale I'll have the 24" iMac in this model number (MA878LL/A). Anything wrong with those models? Entered wrong 24" Model number, my apologies. After poking around, all that seems to be the difference is that the processor is slightly slower and maybe something with the video card?