Look into SMC batteries. They have very good packs that not expensive and perform very well. $70 for a 6500 60c battery. Lots of guys that are way faster than me run them so I figure they are good enough for me.
I don't think you need as high c rating when you go up in cell count. It is be beneficial to have really high c rating in low cell count, high stress applications like SCT but not as necessary with higher cell counts.
Hope this helps.