While the SLI-80 has quite a bit more power than the 300SEI, the 300SEI, if used properly, is a cleaner amplifier that will rival the best in terms of sonic clarity. The difference in sound, of course, occurs between the more versatile push-pull circuit that splits the incoming signal into positive and negative phases and the single-ended circuit that amplifies the positive and negative phases at the same time. Although clean and full bodied, the push-pull will sound smeared compared to the single-ended amp. However, if the 300SEI is paired up with the wrong speakers in too large of a room, it will not sound good; dynamics will be severly limited and the amp will run out of steam. If you have an efficient speaker (92db) with a fairly benign impedence that does not drop below 4 (preferably 6) ohms, the 300 SEI will sing and far outclass the the SLI-80. For the money though, the SLI-80 is an outstanding value. In short, you can not go wrong with either amp. Set up properly, both will produce excellent sound. Ultimately, I prefer the 300SEI. I have compared the two extensively and have owned several Cary products, all of which have been great.