Hardware for numerical calculations

Hello, thanks for taking the time to read my question.

I am looking for a new system at home to perform very heavy numerical calculations. The system will also be used for CATIA design work with intensive surfacing designs.

The majority of work will be numerical mesh generation, computational fluid dynamics and other similar areas of calculations. At work I have a very powerful supercomputer that is used to solve my cases but I need something at home to do other stuff.

I don't want to go crazy with money, so something middle of the roadish perhaps. I have built my own stuff in the past but this time I will probably buy one because it just has to work.

I am looking at some i7 systems at the moment. It seems that built systems on ebay are cheaper than if I were to purchase the components myself and build it.

What do people think of this system for my needs?

http://cgi.ebay.co.uk/GALAXY-3-PC- [...] 286.c0.m14

How would a GTS250 graphics card compare to the 9500GT listed in the above system? It is available similar with the GTS250 for another £25.

Also, some of the software licensing I have is only for the 32 bit version of the software, is it still possible for these to run on a 64 bit machine?
I am sorry if it sounds silly but computer hardware really isn't my area, I just use it to solve what I need.

Thanks a lot for your time.

I'm sorry if this is in the wrong section but it wouldn't let me post anywhere else.

I use Mentor Graphics on my PC, but it didn't work on Windows 7 64 bit edition, so I had to downgrade to XP.

Try getting a system with the same OS you have at work, that way you're certain that it will work.

Theoretically it should. But my experience is that it doesn't run all the programs properly.
Why do you want to use the 64 bit version?
Design software is not very flexible stay with what already works for you.

If you still want to get a 64bit system try your software on someones computer that has a 64 bit system, that way you won't pay for the OS, and then end up replacing it with the 32 bit flavor.