I would go with the Tiger 2. I started out with a NexSTAR also. As long as you have taken off the air brakes and leading edge extensions and are flying that plane to the fullest, then you shouldn't have a problem. Just get someone to buddy box with you for a flight or two because the aileron throw is going to be totally different! It will surprise you, if you not ready for it.
But you will love the Tiger 2, and you definitely will not get bored in a month.

Another reason why I think a Tiger 2 would be good at your stage: You are already learning enough new things (like low wing, fully symmetrical wing, faster plane) that the Tiger 2 can be set up as a taildragger or a trike. So I would set it up as a trike, and then, before you get your Funtana, then you could convert it to a taildragger and learn the basics of taking off with a tailwheel.

Oh, and you can get parts for the Tiger 2, just like the NexSTAR, but they're kind of expensive. (85 for a fuselage, ouch!) You just have to buy them direct.

http://www.carlgoldbergproducts.com/tiger2arf.htm

Hope this helps.

Joe