if your arcam is as i remember arcam being (slightly warm, laid back), then I suspect the monitor audio gs10 would be a nice combo. Just a few hours ago, i auditioned a pair of Quad 12l w/ my sugden amp (a48b). The quads were not broken in, but i suspect that even after they open up, theyou would not sound as open as the Monitor Audio GS20's i heard immediately thereafter.
If the GS10 by monitor audio has the same sonic character, i suspect it would match up well w/ your amp - better than the Quads.
If the GS10 by monitor audio has the same sonic character, i suspect it would match up well w/ your amp - better than the Quads.