The 360 went through several 'quiet' updates. The latest version is the Jasper that should fix alot of the problems the earlier models had. I don't think you can buy any of the older models anymore since the current model is nearly a year old now. But here is a handy page what too look for when hunting for a Jasper:
How to spot a Jasper
Apart from that. Don't buy an arcade model without a HDD. Other than that it's just the color and the size of the HDD.
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My dream setup would be to have BoP in my hands. Some cold wine in the fridge and no appointments. Sadly i fail at two. Do have some wine tho.