DA,

Yes the SIG Something Extra would be a good second plane but no for 3D. As was mentioned the UCANDO series is much better for 3D. Yes the 6102 has enough for what you want to do. That is one of the better 6 channel radios out there. I know, I had one until I went to the 9303 but that's because I moved up to planes where 6 channels were not enough.

I would fly the snot out of the trainer first. At this point you are only flying on the SIM and really have not done the more advanced aerobatics. Yes a trainer will do them, they will not be pretty but that's a good thing because you want to try to make them look good.

I actually had 2 second planes at the same time. The day I went solo I bought a Twist and a Four Star 40. Took me a week to get the nerve to fly either of them. Once I did I still flew the trainer now and then and as an instructor, I like it lots when I get a brand new student that requires me to have to land and takeoff for a few flights.