We have a 12Mbs (12 million bits per second) per hardware node limit and a 30Mbs network limit; we do not have a per-connection limit. If you are experiencing lower rates than this, it is due to network devices/connections between our network and your location. (By way of comparison, a typical cable Internet connection is approximately 3Mbps.)
If you need more burstable bandwidth than 12Mbit minus the other traffic on the hardware node you would need either a dedicated or colocated server. We are able to set the server limits to 30Mbit and also raise the network limit for individual dedicated/colocated servers.