I own an SLI-80 Signature and have nothing but praise for it. As Cruz123 points out, the flexibility of this amp is impressive. Headphones. Sub out. On the fly shifting. The output and signal path tubes are fun to roll and experimentation really pays off. I keep a few sets of KT88, 6550 and EL34 on hand for different moods. The amp is simple to bias, and runs quiet. It's well built and reliable.
For more umph, however, you might want to find a SLAm 100; they appear here occasionally.
For more umph, however, you might want to find a SLAm 100; they appear here occasionally.