Most things in your list are massively overspec'd.... this is a case where more will give you absolutely nothing whatsoever, save your money!
You will never need anything even approaching 4GB on your core. 2GB is probably overdoing it for most people, even when using it as a Hybrid! I would be seriously surprised if you were going to put enough hardware in your core to warrant a 650W PSU, but that's your choice. The 7600 GPU is good, but even my 7300 over does it. On NIC selection outside Intel chipsets, you probably want at least to check someone else has it going, or on their web site that there is a Linux driver available for kernel 2.6.22-14, as the kernel is getting on a bit now. Make sure that whatever sound chipset it uses has an ALSA Linux driver for the same kernel, better yet chose a mobo with a chip that has already been proven to work with LMCE 0710. If you plan to use this as a dedicated core, then the high end GPU is unnecessary.
For your MDs, consider the ASUS Eee Box, a tiny, ultra low power, nettop unit that works well with LMCE and is very cheap. Other than that (and perhaps the MSI Wind PC) I would stear clear of Intel GMA GPUs. Alternatively, you could wait for 0810 (beta) to come out, and have excellent support for the new Acer Aspire Revo that just launched, that has substantially higher specs, uses an nVidia GPU, and is also very cheap.
