As long as your using a dedicated host (not private single server) Generally, good webhosts have so much capacity nowadays ....
And not VPS.net lol, 4gig ram with them is equavalant to 1gig elsewhere. I was with them for over a year and it was the worst experience ever. I also had mediatemple, etc and could compare very accurately that VPS>NET suck.
I like wpengine at the moment(I favor wordpress as cms) and those guys can sure take on some serious server load. And one less thing to worry about - updates, caching, etc etc etc. Guess you get what you pay for.
Agreed, good times, and only getting better.