It looks like the Sonance was made by ATI for Sonance company. The older ATI amps tended to be very strong muscle in the bass, but tended to be somewhat bright. I have also heard that you need to turn on the volume pretty high before you get the dynamics. My gut feeling is that the Sonance will not be as good as the Outlaw in sound quality.
Quick question. You said you are connecting from a computer using digital optical cable. Are you using the toslink output from the computer motherboard? Or are you using a toslink output on a soundcard? If it's a soundcard, what is the exact brand/model of the soundcard? Also, what operating system are you running? (i.e. Windows 7, Linus, Mac OS 10).
Neutral amp to a warm speaker will obviously be somewhat warm.
Warm amp to neutral speaker will be the same.
Warm amp to warm speaker will indeed cause an even more warm sound.
Different pieces of equipment can compensate for each other (like pairing a bright/cold preamp with a warm amplifier). With a warm preamp you can start to lose resolution in the sound waveforms. It is important to know that once you start losing resolution, you can never get it back. For example, if you have a very warm preamp, putting a high-resolution amplifier and speakers will not "magically" bring back the resolution in the original waveform.