For that amount of BW you will want to talk to some of the big guys. I have a dedicated GigE line at
www.techiemedia.com and can't be more pleased with the prices, Quality and support they give me. I have a load balancer and 8 servers and I do approx 600+ megs but do have bursts up to 900 megs on heave traffic days. These guys rock give Jim a shout and see if he can hook you up.
