For a decent nitro RTF, you'll have to bump up the budget a tad, especially if you factor in field equipment. The Avistar has just a little dihedral and a semi-symmetric airfoil, so it will be more fun than the Tower Trainer, but almost as easy to fly...

Avistar RTF:
http://www2.towerhobbies.com/cgi-bin...I=LXMU53**&P=0

Tower RTF:
http://www2.towerhobbies.com/cgi-bin...I=LXCXF4**&P=0

Here's an electric that I've heard is pretty good... it's large enough to be flown in some wind...

SuperStar EP RTF (elevator & rudder only):
http://www2.towerhobbies.com/cgi-bin...=LXAWF5**&P=ML

SuperStar EP RTF (with ailerons):
http://www2.towerhobbies.com/cgi-bin...=LXJKU3**&P=ML

I'd get the one with ailerons, myself...