If you are just doing file services, you could go for an older CLARiiON, maybe an LC4700 and stack it on top of a few Dell PV-630s. You could add more PV-630s as you go, and if necessary start a new stack down the road with another CLARiiON. I'm not sure how much 630s are going for these days, but I'd think they'd be rather inexpensive.