I will tell you all a big secret: There has not been any value in paying for a T1 since DSL became widely deployed. In fact in most major markets T1 circuits are DSL because it allows the carrier to reclaim valuable copper pairs.
Bandwidth is only half the equation. More importantly is latentcy(ping). T1 has a much lower latency than cable/fios. Bandwidth is just how much data can be sent. Latency is the speed of data sent.
When you are trading you are sending/receiving small packets of data, so bandwidth is not important. The latency of those packets is crucial.