I'd recommend:

Que Computers
2323 Hennepin Av E
Minneapolis

The store is cramped but well-organized, computers have a short
warranty, and their call-up support staff is efficient and
knowledgable. 

I have also shopped at The Box Shop near University and Fairview. Larger
shop, a little less organized.

I have had very good experiences shopping at both. For legacy hardware
and aftermarket parts they're on par. For deals on boxes you'll find big
differences between them, and it will vary quite a bit from month to
month.

I'm only a customer -- I have no other relationship with either company.

John Reese