Power should not be a problem. I drive a John Deere 350 sickle mower with a 9 foot blade with my 24 hp Kubota B2400 HST. I think it has 18 hp at the pto, and it does not strain at all.
The problem is the offset weight, particularly with belt drive mowers because the heavy drive head (wobble head) hangs out beyond the outside of the tractor's tires. When the blade is lifted to make turns, etc. the combined offcenter weight of the cutter bar and drive head all rests on the right hand lift arm of the three point hitch. My B2400 could barely lift it, and I felt that I would greatly shorten the life of the TPH. So I built a backhoe style subframe to hold the mower, and it works pretty well.
I am not familiar with the size of your tractor. If it is about the same weight capacity, etc. as the B2400 I think a 6 foot belt drive mower will be too much for the TPH to handle comfortably. But if the mower is a pittman drive, the offset weight is much less; in that case I think a B2400 size tractor would handle it okay.