HP offers some pretty robust solutions for Change Management
So I would guess that their sales reps would tell you to consider one of their products designed to support Change Management. That said, Quality Center has some pretty impressive capabilities and I would not be tool concerned if someone wanted me to implement a Change Request lifecycle within the product. That said, it all depends upon what features and capabilities you are looking for - and of course - your budget!
Bob Aiello, Technical Editor CM Crossroads