I am running a TC3 chassis that started out as a RTR kit. I removed the included stock electronics and replaced with my Airtronics MX-v radio, a Hobbywing XR10 Justock ESC, Hobbywing V10 G2 21.5 motor and added a front spool in place of the ball diff and my car is extremely competitive.
Those others are nice too, and the BT-4 is really a Team C 4wd chassis re-badged by HK.