Well a server with specs is going to cost a fortune either way you go. Stead Fast Networks
www.steadfastnetworks.com co-location offers a 1u + 10 Mbit/sec - $449 . Thats probably going to be your best bet buying a server and going co-location. Your looking at $573 per month for a dedicated server from
www.Layerdtech.com. Buying the server upfront is going to be costly but if you plan on running it for 4 years its going to more than pay its self off.
