I'm not sure if an f4 lens is going to be all that useful to you when you are doing concert work. I used to shoot concerts for a daily newspaper from the pit in front of a stage and used an 85 f1.8 (full frame) at ei 1600 and got shutterspeeds in the 1/500 second range. The IS will help with camera stability, but it does nothing for subject movement. SInce performers like to move around you'll need some shutterspeed.
If you can get closer I'd suggest the 135mm f2. If you can't then the 70-200 f2.8L might be a good choice. I have the non IS version of that lens and use it with a monopod - kind of do-it-yourself IS - but I'd use the IS version on a monopod anyway, and the 300 as well. They may well be hand holdable but I see no reason to use an unstable base as my arms tire, just to prove that I can or can't hold the thing steady.
Finally with the 70-200 f2.8 you could add a 1.4 converter. That'll take the 200 to 320mm and you are back to f4, but hopefully for other things. I'm guessing that the price of the 70-200 f2.8L (non IS) with the 1.4X is going to be about the same as the 300 f4 and the 70-200 f4L IS, and in my opinion the 2.8 version is a MUCH better buy. IS gets you platform stability, but so does a monopod; while but aperture gives you that shutterspeed to stop movement.
"There's never time to do it right. But there's always time to do it over."
Canon 5D, 50D; 16-35 f2.8L, 24-105 f4L IS, 50 f1.4, 100 f2.8 Macro, 70-200 f2.8L, 300mm f2.8L IS.