I think it is appropriate to post some test results from an independent test lab (DLG/Germany) for (stock) saws mentioned in this tread:
MS660; 5.2 kw/9500 rpm; 6.0 Nm/6000 rpm; 7.3 kg
385xp; 4.7 kw/9600 rpm; 4.9 Nm/6000 rpm; 7.1 kg
D.7900; 4.7 kw/9500 rpm; 5.1 Nm/7200 rpm; 6.4 kg
MS460; 4.4 kw/9500 rpm; 5.4 Nm/6750 rpm; 6.5 kg.
Personally, I have no experience with any of this saws, as a 20" dbh tree is a very big one where I live.
I even had trouble justifying my MS 361W.......