Thomas, I'll do a good sitdown comparison of these two in a desktop application for you soon.
But to respond briefly, while I've always recommended the Sex amp for desktop use, its partially because of the implied size, budget, power, and microphony constrains of a typical desktop setup. But if your considerations arent so constricted, then other options definitely open up.
In small to mid sized living spaces, the Orcas work really well with 3-5 watts as well, be it 2A3, el84, El34se, low power solid state and the like.
But I personally (and many people tell me as well) that the 2A3 or 45 tube is probably the easiest and ultimately the least expensive way to "get there." The 2A3 is the cleanest and funnest sounding "mid power" triode available to use with many speakers, and the Stereomour does the tube justice like few other 2A3 amps I've heard at any price, with the other most obvious next step up and frankly off the ladder entirely (at least for me anyways) being the 2A3 or 300B Paramount, also in Bottleheads lineup.
The continued commercial success of these models should come as no surprise. We are all lucky that these guys are pushing the performance to price envelope with these classic triodes so far in the modern day. In a sense, they've been under continuous development for 90 years. Just like Bach, theres a reason people keep coming back to the classics. Feeling great thanks for the beautiful music we have to share with our family on this wonderful thanksgiving day.
Clark