The 4600 will work for 3s, it's within the RPM limit of the motor (although you can't say the same about the efficiency). The 4600 will also work well on 2s, as that's what Batfish used in his Jato with the Lehner 4200XL.
SH Z-Car, Custom Crawler, 8s Savage, 12s XTM XLB 1/7 buggy, 4wd 4-link rear/IFS Pro4 truck, Custom Hyper 10 Short Course, Belt-Drive Mammoth ST 1/8 truggy, 4s 17.5 MM Pro HPI Blitz
Hmm. I thought those motors were efficient at higher than 40k rpm for some reason. I'd like to have decent runtime and high speeds, so I'm going to need something that has enough torque to be geared up without heating up. I'd rather go with 2s since I have 4 e-molis, but am afraid that current will be too high and I won't get the runtime I want (~30 minutes), so that's why I was thinking of using 3s. Although 2s will be lighter and the truck weighs hardly anything at all...