Like marctronixx, I've used a number of different headphones but find the set that came with my One give the best results so I'd say you are doing the right thing to get the HTC ones, you can also be confident that they will fit properly.
I've used Sennheiser CX 300 and although I wouldn't say they were flat and tinny the HTC set give a noticeably better sound.
Good luck.

I've used Sennheiser CX 300 and although I wouldn't say they were flat and tinny the HTC set give a noticeably better sound.
Good luck.
