Well, I would definitely describe the Sugden as being on the 'not fatiguing' side of the spectrum for a solid-state amp and it does sound warm, BUT ideally I think you should try to hear it with your speakers. It's got a very rich, syrupy warm sound that may or may not work with your speakers. Perhaps one piece of information that might be useful to have is the type of music you prefer and the sound quality you prefer in audio equipment.
The Belles has a tonally more neutral sound than the Sugden. A more expensive option might be the Pass 25-watt Class A INT-25 integrated.