I would consider a workstation from these brands:
HP
Lenovo
Alienware (has been bought by Dell though)
Boxx
Workstation Specialists
etc.
I havenīt listed all of them. Some of them might be overkill (like SGI).
Unfortunately I donīt have any experience with these manufactures, I donīt know how good their service is etc.
You could try sending each company an e-mail or calling them saying that you would like a reliable workstation with good and fast support and troubleshooting, how much performance, what parts etc. you would like it to have, what you will be using it for and what is your budget and than compare their offers.
Of course it has its caveats. For example if they say their support is top-notch you wonīt know until itīs put to the test.
Just an idea. Good luck with your hunt.