Nikon D700 out of the question?
For some of your pics, I find the noise quite acceptable. And with a NR software like noise ninja, you can reduce the noise drastically. And on top of that, shoot in RAW and do PP. If you still cannot live with that, and must shoot in ambient light, FF is the only way to go. It has nothing to do with whether you are a pro or not. But it depends on what you can or cannot live with.
since when must have skill to justify FF?
I thought it was only whether or not one had enough $$ ?
like dat I'll never be able to get FF, coz no skill....
If you are going to shoot another event, why don't you rent a FF-body camera, and get a similar fast lens for both your Sony and the rented body. Also, rent a flash at the same time for your Sony and see if it is worth getting it full-time. Then compare if you are happy with the outcome.
Only then will you know if you really need a new body or not.
Just my 2 cents.
A picture a day keeps the blues away!
K-X is better than K-7 on high iso noise handling...