I've been googling a bit and found that acer veritron s480g does support Core2quad processors, so you can find any quad to upgrade your core2duo. And I found on one Russian website a selling advertisement of the same Acer veritron s480g with x5667 Xeon, so it can lead to that its possible to run a Xeon on your rig. It's really cheap, about 25-30$ for E5450 on eBay or Ali usually with free shipping. However variant to go with 1366 platform for around 200$ is great too.