SPCR

Last year I built a Phenom II X4 945 system in a mid-tower case but it's been sitting in my parents basement because carting around a desktop doesn't make sense for me as a student. However, now I'm getting the urge to have something more powerful than my laptops but it has to be small. So, my question is should I transplant most of my guts from the AM3 build into a mini-ITX case with corresponding motherboard, or would I be better off starting from scratch with sandy bridge? Cost and quietness are the main issues here, I think I can recoup around $400 if I sell my box whole and obviously less if I'm only selling the MB, case, and maybe hard drive. Also I would be looking at using a DC/DC converter in something like an Antec ISK (cant decide 100 or 300).

Excuse the incoherence, it's 3am.

tl;dr: I have an AM3 system, should I canibalize parts from it to build a cute little mini-ITX box or start from scratch with Sandy bridge?

ETA: I'd be looking at something at least as powerful and most likely jettisoning the HD4850 that's in my AM3 system. Applications for the box include HD video streaming, transcoding, software development, and virtual machines.

Also, as far as a Sandy bridge setup I would be looking at a board with dual digital video outputs, and an i5-2400S. I'm currently considering the ASUS P8H61-I. Lack of integrated wireless is a concern to me, but I could always put a USB wireless card off an internal header and run antennae pigtails. (I hate having dongles stick out the back of my computers.)

Unless you need more CPU than the 945 has to offer - why not recycle?

If you're looking for more GPU power - the MSI HD 6870 Twin Frozr II is fast and quiet.

The 945 was great for me when I did use it. Im considering starting over for efficiency reasons, my concern is that the Phenom + 4850 or even without the 4850 will be too hot to cool quietly in a mini itx case. I could go to a sugo or q08 instead of isk or mi008 but those are also less small.