Sorry,
Yeah I realise it's not really related to your problem, it's just something I found interesting when I learnt it at college. I was just trying to point out that the difference in level between 50w and 100w is not very large, which is something I think people don't generally expect. Differences in the speaker and valves etc. even if they're the same model, could easilly make up the 3dB difference you'd expect to find between the50 and 100w amps.
Cheers,
Spud.