Comparing specs....
25W/8R vs 60W/8R is a significant difference. ~4 dB. When you want to crank it up w/o running into audible distortion, it could mean the difference between loud enough & not loud enough.
The Arcam has a higher SN spec: 117 dB(A) vs 103 dB but weighting not specified, so maybe w/o weighting. Amirm measured 105.7 dB SN through the digital inputs. Again, not sure if it's a weighted measurement. Also not sure if the difference is meaningful; ie, I hear virtually nothing from the speakers when I pause play with the Wiim Amp. Even if the Arcam is quieter, does it matter?