there are several ways of specifying signal to noise ratio with a big difference being if it is at 1w or "below full power". if at full power, you have to subtract the amount of the power for comparability.
example: the mark levinson no. 53 s/n is rated at -85db and the behringer ep4000 is rated at -100db.
so how does behringer beat mark levinson?
the ml amp is at 1 watt. the ep4000 is at rated power, which is 450 watts. 450 watts is 26.5db higher than 1w, so subtract that off the behringer. the behringer is now at -73db s/n, which is 12db less quiet than the mark levinson.
a weighting, no-weighting, 20hz-20khz or 1khz, use of the "greater than sign", are also other ways of confusing the matter.
so, just be careful when making "quick comparos" with respect to s/n ratio.