I have only heard good things about Isprime. You can't go wrong by dealing with them.
I also have servers at
www.mach10hosting.com and
www.xxxwebhosting.com . My main servers are at Mach10. The servers at both of these companies is superb.
Another company i can vouch for is
www.National-Net.com Great service!
You can't go wrong with either of these companies!