OK time to chime in I suppose, First thing to look at is the capacity not the C rating, the capacity is in effect how much go juice is in the tank, you can buy some pretty sweet lipos cheap with around 5000mAh, the C rating is its discharge rate and sorry to everyone without degrees in electronics, but with the standard cabling in RC you would be in trouble with a 40C 5000mAh burst.
Now lets do some maths, say if you completely
drained a 5000mAh pack in a 5 minute heat, that means it can sustain a constant current of 5 amps per hour so lets average this out over a heat, 5 mins is 1/12th of 60, so to drop a pack completely in 5 mins you would be drawing 5000mAh x12 which is 60 amp continuous.
Then we will double that just to be generous and you will have bursts of around 120Amps. now 120 Amps at say an average of 7Volts will create 840 Watts of energy, now go around your house and start comparing all your appliances and you will get where I'm comming from.
Also increased temperature in packs reduces voltage due to increased resistance , google temperature coefficients, unless the pack was completely made from carbon.
All in all when it comes to buying a pack start by getting a 5000mAh pack and then as long as its over 20C then you will be fine, unless you are super pro and drive on rails with absolutely no variation in consistency.
RC mushroom has the zeppin lipos for $27 usd, I have a couple and run 13.5T super stock, I am competitive and usually have a consostency of around 0.3 which isn't bad considdering the super low traction we race on.