How did you spend $200 on a Stryfe and NOT have any LiPo gear?
You might be able to get away with a NIMH or NICD pack, but NOT IMR's. Bert81 gave a very generous discharge estimation. You should probably assume that IMR's discharge 3-6 amps.
Also, using 3 IMR's would be overvolting the motors, which would cause them to run at 50K RPM, which unless you have a high crush cage, isn't optimal for performance.
If the entry cost of LiPo tech is discouraging you, the Turnigy E3 costs around $10 and can balance charge 2s and 3s batteries.