Best motor for 1:10 truck on 8 cells?

[Rtsbasic]

Thing is, will the 8s or 9s be slower than my 6s on 8 cells? I know the whole system will be more efficent and cooler, but as I only run in 5 min mains when racing, and for bashing am rarely at WOT runtime isn't an issue. The motor is coming off a 5 min run at ~45C so isn't very hot, but if I gear up I loose too much acceleration.

Spending bigger money on a motor isn't too much of a problem, I looked at a Lehner XL and think that might be a good choice, but have bad experiences with Lehner Basic's.