Try InfoRelay (www.inforelay.com
) -- Rusty500 is one of their reps on this board.
They have two data centers in the Washington, DC/Northern VA area. One might actually be in DC, but I can't remember.
They also have some high-end SAN stuff as far as remember, as well as load balancing... I had them quote me on a project similar to yours, and I currently host almost all of my high-bandwidth stuff with them.
Excellent service for the past several years... stable company, great support, and a great network.
I don't need managed hosting for much, but I am now working for a client who was hosted at RackSpace. They ended up moving to InfoRelay... saving a bunch of money and getting better support/management.
If you don't need managed, you can definitely save money by going to someone like EV1, but I would strongly suggest InfoRelay for high-bandwidth or clustered/managed applications.
Feel free to PM me with any questions.