Best controller for 12-16 cells?

[Rtsbasic]

After reading from a few people about how long MGM take to resolve issues, I am staying as far away from their units as I can. Which is a shame, I come very close to buying a 16016 when they came out with the cube design last year.

Serum, the reason I act like its going to break is because every brushless ESC I've owned has broken in some way with the exception of 2, generally it'll fall apart or let its smoke out. I treat my equipment as carefully as I can, but I bash my truck hard and except components to fail eventually. Its nice to know that if they do fail the warranty is there to fix it.

nitrostarter, whats the temperature like on your setup with that gearing? Sounds pretty much exactly what I'm looking for - top speed in the 40's and good runtime.

Whats the most cost efficent way of upgrading the diff's? I see the "bulkless" gearboxes on RCM for 1/8 buggy diff's, but I simply cannot afford it. What other options are there? I will be picking up the steel idlers when I purchase the 9920.

For the min I may get the 9920 and run a 540C 9L on 14 cells (been offered a direct trade for my 540 8L, simply because its a tad faster than my mates truck with his 9L). Then when budget allows get the 7XL. What would the power difference on 14 cells be between the 9L and 7XL?

Thanks for all the help so far, very informative :)