I own 3 GTS's. One is in a T4 running a 12 and 13t motors. Never had a problem. Really good bang for the buck. I'd buy another.
My opinion only...........The 6v BEC is overrated. I couldn't tell any difference when I replaced an older Tekin with a 5.6v BEC with the GTS's 5.0v BEC. Get a good servo and don't worry about what voltage the BEC is..........
If you are used to wildly overpowered nitro cars, you may want more than a 19t motor. But 19t will be mostly competitive in mod on an outdoor track, at least at the ones I run at.... Since you have nothing at the moment, you may want to consider brushless, it's is cheaper in the long run.
Don't worry about the discharger and/or equalizing voodoo. You can't put down all the power with a 2wd car/truck on an outdoor track. You don't need the last milliwatt of power out of the batteries..... Charge, put in car, run car. Repeat.
Get the cheapest matched packs you can find. Promatch usually has some good deals. Again, you don't need killer packs for outdoor off road 2wd.
If you are running indoors on a super high grip track, then things change a bit.....
Go have fun with the "plug n play" electric..........