Need some lipo size help here

Ok, I have another question here. How should I do this?

Buy a 8.5 (9K KV) and run 2s lipo (64,800 RPM)
Buy a 10.5 (7,300KV) and run 2s lipo (54,200 RPM)
Buy a 13.5 (6K KV) and run 3s lipo (66,600 RPM)

Which way should I do this? Im running a mini on a full size track, so it needs RPM, and from the beta testers, even the 9K KV motor runs real cool because its 380 can.... But doing a low KV, high voltage, im thinking I could get more run time off a lower MAH lipo?