Just FYI, all Lipos can be charged at 1C. Some claim to be greater than 1C capable for charging, but in reality that's possible for all Lipos. Usually, greater than 1C charging is only recommended when either the charger has a built-in balancer or the balancer can communicate with (and alter the charge rate of) the charger, like the Thunder Power charger and balancers. The most important thing to consider when working with charge rates is if your charger can handle what you want to do.
The next size up in Enerland cells (the company that makes the Flightpower cells) is a 5000mah cell. This cell is a true powerhouse, it can sustain 30C currents (150amps!) pretty well, but is rated at 20C continuous. However, this cell is priced around $60 PER cell. I think for you Enerland cells are out of the picture (for cost vs. capacity).
The True RC cells have a graph that can be seen here:
http://www.rcgroups.com/forums/attac...hmentid=806053
Don't worry about the ending of the 6C (green) curve, that was just when the temperature cutoff cut in on the guy's testing equipment.
This cell is about a 8C continuous cell, but is capable of doing 10C for most of the discharge. There's no way that your car is going to be pulling 80amps average, so the discharge rate is fine.