Did some research (was fun and made me drool alot) you should go to the Tyan.com web site and check some of the vendors under 'where to buy' most have a configuration of options for the 4 cpu & 8 cpu systems (AMD only).

The 4 cpu system uses dual or quad core CPUs so you can get up to 16 cores and double that in the 8 cpu system totalling 32 cores. They mention 6 core models but there isn't any specific information about doing that.

Once you start going multiple CPUs (and the ram that goes with them) the money starts adding up fast. I think most of the sites are a bit inflated in price for ram/CPU/drives so could possibly order barebones chasis and buy the parts cheaper and install yourself. Check newegg.com for component prices (especially ram & drives).

8 cpu (32 cores) with 64Gb Ram 2-1tb hard drives came in about $9900
Good thing it does support enterprise editions of Windows or Linux for compatability.

Check out some of the configurations and see if this will suit your needs...