I could not wait so I bought the TC-50. No big deal as I also have two RA100's. As for the power soak, I rarely ever use it in the RA100 but once in a while I have. Seems to work best with SED =C= EL34 tubes, it is okay with the stock EL34's. So far the stock tubes are great in the TC-50. Have not put the NOS Siemens in since the amp came back from Mesa. Had issue with the mute circuit latching on due to a triac issue. Other than that the TC-50 has been good to me. Still, wonder what 4 6V6's would sound like, as it was the 6V6 option that sold me on the TC-50. Tempting. I did not see a half power mode on the back or front of the TC-100, other than the power soak feature. A half power mode would be cool if it had it. I doubt I would want to sue the power soak for that as it becomes hard on power tubes and may result in shorter tube life with the more aggressive attenuation settings. However, the trade off is operating at ideal saturation levels with reduction in output so you do not have to go deaf to hear the sweet spot. I have found myself using the RA100 at full power more than using the power soak. CH3 at 100W on the TC-50 would be a bonus as the higher gain settings tend to compress a bit.
Same size as the TC-50 so you can use the Vertical 212 cab if you have one. Can't mount the RA100 head on top of that as it is huge in relative size, almost larger than the OS Recto slant cab but fits with a slight bit of overhang. Having the selectable FX loop, reverb and 3 channels with solo function on the footswitch may be more ideal and a means to edge me away from the RA100. If I get the TC-100, I have no plans on selling my RA100's. I do not mind having both.