I like the A38, can't say the same for 28 and 18. It would be better value at around £900 though to bring it in line with Roksans K2. If I was Arcam I'd kill the A28 altogether then do a an upgraded, re-designed integrated with DAC which materially at least is on par with other £1000+ amps. Mind you, Naim's XS does'nt look to posh either ...
If I have missed anything Arcam currently does it's because I don't follow any developments as much as I'd like to at the moment. As always, my opinion only.