Hi,
I bought two RB981 amps a couple of years ago,
I paid £100 each (which I thought was a very good price at the time).
I sold them a year later for £150 each.
I would say £275 is easily too much based on my experience.
I hope this helps,
if the 981 is the sterio 2 channel model(130 watts) i purchased 2nd hand for £150 of tag forum and sold for £150 on this forum, about 5 months back would say there are well overpriced.
you could get 985mk1 possible mk2 5 channel rotel for approx £300+