I still wouldnt, you can sometimes get certain things running on lower vaults, but feeding too many is running the risk of overheating and going pop.
I almost killed a monitor by using an incorrect power adaptor, I think it was off an old modem or something, I turned it on an it made a realy bad noise, (cant remember what the noise was, but it was like a 'doh, i think i just broke it' type noise) so pulled the plug straight away, and lukily I didnt kill it...
Now I always use the right rated power adaptors!