Looking for a HPC $5-7k
 

this is going to use as a shared computer for our group.
everybody can remote desktop and run matlab or ANSYS fluent.
For fluent we have a limit of 4 licenses for each user (25 licenses total).

I am thinking to get a 2 six-core Xeons and 128G memory

Could we get a dell or some other namebrand with 5-7k?
I guess not.
to build one, for CPU, memory bandwidth is the most important, and how about other things,like clock speed and QPI speed? how much difference between 2.0G and 2.9G for clock speed?

what should we choose for motherboard?

Don't go on my opinion alone (not overly experienced), but unless you see the need to do large FEA work then I think 128GB RAM might be overkill here. Someone might be able to give you a sense for how large/how many Fluent jobs you can run with that, but I think you're CPU will be crawling long before you max your memory on CFD (unless you're doing extremely large models, like maybe the 50-100M+ elements).

Actually, just getting boards that let you use 128GB RAM could be expensive. For your 5-7k budget, I think the money could be better suited in faster processors(/maybe hard drives)

a marked difference going from 2.0 to 2.9GHz.
Memory needs can be determined by your job size.

Linux or Windows?
more info about the job types and frequency of working simultaneously will help. IMO, 4 people sharing a machine at the same time with a CFD solver running for decent size jobs, not much will get done. Your user experience will be poor unless you set the cfd solver to low priority. If you are not running the solver on this machine and 4 people are sharing it at the same time the mesh, pre, setup and post will be no problem.

i am not advertising them but I use them as a sanity check for pricing since they have a good selection and it is faster than looking up individual parts.
http://www.thinkmate.com/Computer_Systems/Workstations
The big vendors will most likely be more.

Thanks man!
We are using windows.
For this machine, no more than 2 people run the simulation at the same time.
I will check the site.
Thanks!