So I recently purchased 2 TQ racing sx10 4wd buggies (1/10). One is a professional kit that needs to be put together and the other is a RTR but i bought it with only a 2.4 ghz controller, receiver and servo. The one pictured below is the RTR. I went to a hobby store to see how they could fit my needs. I wanted to go bashing with it, as well as having fun on the street. It also has to be waterproof. I want it to go over 60+ mph and remain torquey enough to play with. He suggested a sidewinder 3 brushless system. They come with 4600, 5700, 6900, and 7700kv motors. He said that with the size of the battery compartment i could only fit a 2s lipo. the 4600 and 5700 can use 2s or 3s. the 6900 and 7700 can only use a 2s. He suggested the 6900 so I will be back to pick that up and have them solder some stuff onto it and get it running. Does that all seem like it will work well for me?

If you just looking for speed runs and light bashing, get the 6900. Gear it by what castle suggests, then go up a couple of teeth on the pinion keeping an eye on the temps. As long as the motor stays below 160 and the esc below 150, you're good to go. Hope this helps

Thank you for you input, ill keep that in mind