I understand that the specs on this amp state 160x2 @ 4 ohm bridged and they are underrated. I was just wondering what these amps normally put out at 2 channels @ 4 ohm bridged.

You can expect 10-15% extra, on average, from the SAX multi-channels.

=)

I know nothing about electronics, but I was wondering how can it be 4 x 50 and 2 x 160, not 2 x 100 ?

I use my 50.4 bridge, on my component set (rated for 2 x 80 watts), and I don't see my speakers struggle at all ! They seem to like that Sundown power.

(I've set the gains by ear, no DMM settings).

I've noticed a big improvment with the outputs from the tweeters, but not so much from the mids. I use the passive filters.

4x50 @ 4 ohms -- bridged is like 2 ohm stereo operation in power.