I have a similar problem and are looking at a similar solution. The PD range caught my eye too. They are so new, very little feedback yet. I spoke to one guy who had the PD80's, but was selling them as they were too large. He had enjoyed them, but found them lively and a tad bright. I agree with other posts, a steady impedence across the frtequency range is what a SET needs and output transformers are critical. The very good cheap chinese tube amps seem to skimp a bit on transformers, thay are very expensive to produce. I use an 22 watt 845 SET.
Tyler of course, will take the speaker back if you don't like it. You can't say fairer than that. A couple of other small US makers I am considering, are Reimer and Daedalus, both make SET friendly speakers which are thought highly of, you may want to check out there web sites. If you do go for tyler, please report back your impressions, I am sure many of us would be interested.