With your 88db speakers you'll be hard pushed to get a decent upgrade over PL Dialogue HP. With tube amps you need to spend at least double if not triple the amount to hear real improvement with those speakers. SS amps at similar price class are almost all dry and sterile sounding in comparison in my experience - don't get me wrong, they are perfect, but they just do not excite nor provoke you to listen as the tube PL does. There's an extra level and dimension in that tube sound, SS amps just don't hit that spot, at least in this price range.
I also have 85db sensitive speakers so I share the dilemma. Thus I'd recommend another option not covered here (albeit a controversial one but I'll exmplain this below): modify your Dialogue Premium HP.
PLs are indeed well designed amps for the money, for 98% of the cases I wouldn't touch it and wouldn't recommend touching it. But for those those 2% who look for the very perfecrtion there are certain weaknesses that you can exploit to max out their design to fuller potential. With customized tubes you can do a lot improvements, but internally PLs main weakness are the coupling and power tube caps. I recapped mine with coupling V-Caps TFTF. Not cheap, mind. And takes ages to run-in (V-Cap measurements say around 1000 hours to full burn-in , but I noticed considerable improvement around 200-300 hour mark already).
If you have the dosh, consider also the powertube caps converted to V-Caps. There's enough room to fit those lardy caps. Those will be considerable improvement over stock DuRoch caps. I didn't have enough and went for Jupiter Copper Foil caps for power tubes instead.
Those Jupiter Copper Foil & Wax caps are controversial since some people rave about their sound, yet those who have measured them in detail tend to be dissapointed (small distortions measured). IMHO Jupiter cap stands where psychoacoustic hearing preference is set above measurements, hence they have their subtle speciefic sound character, you may like or may not. After nearly a year living with them, I got to say I love their sonics to bits!
After this recap mod and burn-in my HP Integrated took another sonic level and IMHO rivalling amps at a much higher price class. The sonic finesse really impresses me the more I listen and the more I adore the sound. Now I have no plan to sell it, at least within 10 year perspective, unless I find something staggeringly better at this price class among tube amps, which I doubt. So my HP now is probably a lifetime keeper.
So maybe this HP mod route is worth considering for you as well.
Just me 2c,
Margus