Mapman,
I do use an external DAC. What you mean by "tried mod to disable wireless" always adds confusion on the SB forums. So we are on the same page, when I say disabling the wireless mod actually means the wireless radio is ON. When you try the mod and do a tt -s, you will know what I mean. In my setup, I have the wireless mod enabled which means the wireless radio is OFF. I have compared the the two and having the wireless radio OFF (mod enabled) made a big improvement in my system. The music was smoother, less digital hash/grain, and transparent.
Like you, I have never used the onboard DAC only with an external DAC. I agree with you that SBT+external DAC is comptetitive more expensive setups, but the mods did bring the SBT to another level in my system. (**Warning bold statement/opinion coming up**) I truly believe the SBT with the mods can compete with transports costing in the 2-3K range and SBT+mod+external dac competing with CD players in the 5K range.
Another great thing about the mods, you can tune to your liking. I compare it to having different filters on the DAC. With different combinations of mods disabled/enabled, you get a different flavor of sound. Some good, some bad depending on the combination. If you go to the SB forum under the Audiophile section, you will read about the different results and peoples settings.
Based upon your responses and reading your thread on your system setup, it seems you haven't tried the mod. You may have your reasons for not trying them which is fine. I just think you are missing out :)
PS. Not trying to be rude, but don't want to clog up the thread with us going back and forth on why wireless should or shouldn't make a difference. I'd be happy to discuss on a separate thread so we can keep this one on track.