Without more information about the rest of your system, it's going to be impossible to tell if the rest of your system will be resolving enough to be able to tell the difference between using an internal or external DAC, or using a preamp.
My system consisted of an NAD C162 pre, Aragon 2004 amp, Emotiva XDA-1 DAC and several different speakers (Silverline Minuets, Dynaudio DM 2/6, Paradigm Studio 10s, System Audio 505s).
Using my very modest system as an example, I could definitely tell the difference between the Sonos internal DAC and the XDA-1. Using the XDA-1, the highs and lows were more extended. The bass was tighter, etc. Just about everything improved.
Still, if you like the internal DAC of the Sonos, the internal volume control of the Sonos could be a problem for you. It's volume control is within the digital domain, meaning that it cuts bits to control the volume level. At lower volume levels, the quality of the music may suffer.
Of course, beauty is in the eye of the beholder. I'd suggest that you try the Sonos straight to the amp. If you like the way it sounds, then you've answered your own question. I'll also tell you that when I've had to rig up something portable, I've often run a Sonos straight into an amp. I didn't think it sounded great, but it was certainly more than good enough.
My system consisted of an NAD C162 pre, Aragon 2004 amp, Emotiva XDA-1 DAC and several different speakers (Silverline Minuets, Dynaudio DM 2/6, Paradigm Studio 10s, System Audio 505s).
Using my very modest system as an example, I could definitely tell the difference between the Sonos internal DAC and the XDA-1. Using the XDA-1, the highs and lows were more extended. The bass was tighter, etc. Just about everything improved.
Still, if you like the internal DAC of the Sonos, the internal volume control of the Sonos could be a problem for you. It's volume control is within the digital domain, meaning that it cuts bits to control the volume level. At lower volume levels, the quality of the music may suffer.
Of course, beauty is in the eye of the beholder. I'd suggest that you try the Sonos straight to the amp. If you like the way it sounds, then you've answered your own question. I'll also tell you that when I've had to rig up something portable, I've often run a Sonos straight into an amp. I didn't think it sounded great, but it was certainly more than good enough.