all of our sites (2 forums with almost 3,000 members a piece) use imountain.com. they have the absolute best support & their prices are fantastic. they will accommodate your every need (within reason, of course- no illegal stuff) & they really bust their butts. they always get back to you within a timely manner, too. they also use clustered web hosting, which has been awesome.
some of their specs are:
that their shared hosting server has 8 cpu cores & the mySQL has 16 cores (Quad and Octal core, but the absolute minimum is Dual Core)
they use reliable name brand equipment from places like IBM, HP & Linksys.
they always have between 6 and 16 gigs of ram in their servers
they are clustered (which means more reliable & faster)...
honestly... i can't say enough good things about this web host. they are the best i've ever hosted with in my 8+ years of bouncing around from web host to web host... i am never leaving them & if you hosted there, i'm sure you wouldn't want to leave them, either. they're absolutely fabulous!
check 'em out:
http://www.imountain.com/
~ M