at 50K alexa you must seriously consider moving your site on to a VPS as shared hosting will hit you with downtime or suspend your site stating too much resources consumption.
I don't think a shared host will host a site that big. It would cause a lot of problems for the other smaller sites on the server. Go dedicated
Haha! Agreed. But honestly, I'm in the same boat as you, hostgator seems pretty fast but they are very unprofessional in the sense that they set the default 404 page to there advertising + google pub code. Hostgator folks are nice though, pretty decent server speed for the most part, dreamhost is terrible server speed and way oversold but they don't nag you about inode limits like hostgator... Dreamhost will get on your ass for CPU usage, ultimately though, hostgator, they got speed over dreamhost, but these are my only two experiences... hope that helps!