I'd start with the 90 w/ch arcam and see how that sounds first then if still desired 250w/ch or more of good quality Class D meaning robust power supply and high current delivery good down to 4 ohm would be a step up in most cases. Benefits may be lesser in a smaller room and/or lower volumes only.
Arcam is good stuff but most receivers and many integrated amps cannot match separates of the same power rating in regards to power suppl;y and current delivery with low distortion into lower impedances which matters to get the most out of the OHMs.