Let us know how things turn out. I was in the same situation you were in terms of being bored with my trainer after flying for about a month or so. Like you I too was soloing after my 2nd or 3rd time on a buddy box and many members of my local field were amazed at my progress considering the "trainer" I was flying was a tail dragger and was capable of MANY aerobatics due to a modified wing.

Anyway, one of the best things about this hobby is it allows you to do whatever YOU want to do. I now own a GP Venus and should have an Aeroworks 540 60/90 plane at my doorstep this week. Both should provide me with different flying experiences and that extra ooomph I'm after at the sticks. As other people mentioned on this thread just keep that GP 300's rates on the low side and don't even think about slowing the plane to trainer speed on landing and you should be fine. Best of luck and if you can submit some pictures of your plane as I've been thinking of getting one next year too