I have a 505u and play mostly vinyl. Great phono stage and plenty of power - I rarely have the knob much past 9 o'clock. I use Monitor Audio RS8 speakers. I love this amp. Sounds wonderful. I didn't have the chance to compare it head-to-head with teh 507u, but that's almost 2x the cost, so I was doubtful if it was worth it. Highly recommend the 505u.
