The input impedance can be changed by swapping a couple of resistors. For 50K, R11=47K and R12=330K according to information from the DIY forum. I found the amp to sound a bit on the warm side of neutral. While the detail was good, it wasn't great. Certainly more than enough to enjoy the music. Seemed to have a lot of grunt for 6W. The faceplate and chassis are very nicely made. Very enjoyable amp. I'd think it would sound great with Omegas.