Forgot to add temps:

Motor 70ºC
ESC 60ºC
Battery 30ºC
Ambient temp 27ºC

for the 1500kv on 6s you will need a 19 or 20T pinon for track speeds. With the 1500kv motor you will nee a 16 or 17T pinion. I think either motro would probably be fine, but the 1300kv would probably run cooler.

I think the medusa's have different characteristics than the neus and will need higher RPM's to run efficiently. I ran the 1500 in my maxx and couldn't keep the heat down. I had to gear for around 35 to keep temps on the motor under 180. Asheck on the other hand has had great results with the 2000 so who knows. I do think the ambient temps are a major factor as it is always in the high 90's in Houston from April until October.

I run a 1500 medusa 60mm in my hyper8 on 6s. It does get a bit warm. Currently geared 14/46 with the 43/13 diffs and crimefighters. Plenty of power, and very smooth, but the heat does worry me a bit. I may try gearing up a bit, and changing the timing on the quark. I also have a 1600kv 60mm medusa to try. Not sure if the added rpm will help...

New update:

Went this morning through the whole pack in a bigger circuit stopping every 3-4 minutes to check temps, again the 6s pack with the 2000rpv motor, running most of time limited to 75% thought I could hardly get to full throtle...

Ambient temps were around 30ºC (85ºF). Temps used to get at 70-80ºC (160-175ºF) on the motor, 40ºC (100ºF) for the battery and 65ºC (150ºF) for the ESC... even one time the ESC went up to 80ºC (175ºF) ... too hot.

Again... Went thru the pack stopping every 4 minutes cos the esc likes to come up to 75C (167F), don't know if it will be better with the 1500 one when it arrives... Any ideas?

Amb 30C (85F)
Battery 34C (90F)
Motor 80C (175F)

the higher KV motor(2000) will pull more amps (increased heat), so in theory it will run cooler by going to the lower KV motor and should enable you to run more WOT which is better for you ESC. You will pull the most amps punching from a stop

Last update:

Modded the case of the mmm (removed the top) and zip-tied a heavy duty fan... therefore the ESC is now around 120 F, going to keep the fan while I wait for the 1500 medusa, the 2000 is running hot on 14t

Btw the fan is taking around 0.25 amps...

I got the new one peice battery tray for my rc8 from mike and I can now fit a 4s 6000mah poly with a little room to spare about 1/8''.