I am brand new to mac being a pc guy for years.I do audio recording.Now, I picked up a very cheap used mac pro g5, single core. How bid a deal would it be to upgrade processor to dual. And/or is it not cost effective.The single will work fine but if I can fairly cheap...well then maybe. Oh, and( maybe dumb question here) the used machine I mentioned takes 400mhz pc3200 memory. Looks to be the same as my windows pc. Would it be? Is there a difference between mac and pc memory?