If you can afford it go brushless. The EZrun is really good value: i have 3 in different cars. There are better but you'd have to spend big $$$ to get a better system.
I honestly wouldnt spend big money on a TT01, or spend too much on upgrades. You can easily end up spending far more than the car is ever worth & a TA05 or TB03 would have been cheaper. The EZrun is still a good choice for that car though.
A metal driveshaft & bearing kit, 2degree rear hubs are all you need for now.
Perhaps a harder metal pinion than the standard one as well.
And some good tyres.
Brushed motors can be a bit of a pain. The motors need rebuilding too often: its cheap & easy but just a pain in the A. You need to find a shop with a comm lathe.
You can find anything on ebay, if you live in the US then you're in parts heaven compared to some other countries.