Yamaha MX-1000 Whats it worth?


I have the chance to purchase a Yamaha system with a MX-1000 Amp, TX-497 Tuner and CX-630 Preamp. The amp has a problem with channel B or C not working, something i would end up getting serviced. So what is something like this worth. I was thinking about offering 600 dollars.
cirtcele