Thank You for all the tips, and for links to those stores, I didn't know there are so many options for those tanks
I'm looking at the prices right now, and i think I will go with the S&S version.
It costs 200$ and has metal tracks, smoke and that upgraded RX18 electronics, and from what I see, if I wanted to add metal tracks and the board later on i will pay more separately than buying it from the start. It would be 100$ for the basic tank, 75 Eur for metal tracks, 20 Eur for RX board and 17 Eur for smoke module - So i would end at 223$ + shipping + metal gears.
Will the RX18 work with this gearbox
http://www.rctank.de/41-PRO-steel-ge...-motors/18000t ?
And another question - i see RX18 and RX18 2,4 Ghz electronics - is there a difference?
I'm sorry for so many questions, I get confused by the amount of available parts
"
Someone mentioned in my intro thread that this was a money pit of a hobby" - I have just finished my new sniper rifle for airsoft - it cost me almost 1500$, and earlier I spent a lot of money on WH40K army, so I think that every hobby is an endless money pit 
Edit: Or maybe I'll go with the basic one, and upgrade the electronics (just need to find one compatible with that Pro gearbox from rctank) and get the T-81 tracks... I hate having so many choices