Just noticed on a site in the UK that the GWS E-Starter has been discontinued over here anyway, if that is the case will make it hard to get parts if you need them.
I had the Multiplex Minimag with a GWS Brushless whcih needed a few mods to the engine mount to fit, absolutely superb plane and gave me the stick time I desperately needed and got to the stage of throwing it around in the air, inverted, rolls etc, I was going to upgrade and the guy at the model shop suggested I up the throws before I did and slowly edge the CoG back before I went to the next level which I did little by little and made it more responsive and the rolls flatter / faster.
You say in the future you'll only have 3 channel you may well suprise yourself, I though I'd be the same and have a warbird but once you master flying round in circles what do you do then, I now have a Multiplex Acromaster and can do most aerobatics and am trying to learn to do 3D.
If you've already upped the throws on the Decathlon and have loads of simulator time you may possibly be able to go to a Multiplex Gemini and set the rates lower than the instruction manual says but you possibly run the risk of destrying it on it's maiden if you've never flown with ailerons before !!!!!!!
Good luck and happy flying whichever you decide on !!!!!
Neville