I can only say 1 thing, why people want to sell his HU if no problem? Unless he is sincere enough to tell you what is the problem. Like me, I will sell my HU when there are some problem.
Anyway I can say that P7750 is a value for money HU as it has 3pre-outs and OEL with screen saver. The display also not that bright compare to other brands. Only the down part is blue colour.