Combine Multiple Broadband Connections On Single Network?

setting up a simple internet plan for a place, but a LAN center needs crazy fast internet, faster than most large enterprise class offices that take up an entire floor or two. Otherwise there is too much lag in games like first person shooters. We are expecting to have 60 computers, plus people bringing their own gaming rigs from home and laptops as well, xbox, ps3 and other consoles, all accessing the internet at the same time to varying degrees, with no room for lag. There is a LAN center in california that has 200 or more computers and they pay for 9 t3 lines, which is thousands and thousands of dollars per month. Plus the initial equipment to set that up from what I can find on cdw is many thousands of dollars also. Something like 10,000 for a router with 4 expansion bays, and 4000-6000 dollars for a t3 expansion card, bringing the total to around 22-28,000 for equipment to do just 4 t3's. Plus the monthly cost. Since we don't need all of the traffic to be secured like a high end business class line like a t3, I was considering what it would be like, and how one would set up, having multiple cable internet lines coming in. They make cable wic cards for cisco routers. 4, 50meg cable lines would give us 200 down and 40 up but I don't know how to make that work without having multiple public ip's. I was thinking that if I did have multiple public ip's on the network I could just divide the computers up so that they are in groups, using all of the public ip addresses for gateways, so that the load is split pretty evenly, but still, there should be a more seamless way to do this, I just don't know what it is. At the rate for business cable internet, 4 lines would probably only cost around 700 dollars a month, which is much better than probably 5 grand a month for several t3 lines.