So I just bought a Hegel H390 and

I would posit that the Hegel is such a neutral amp that it's really going to be the speakers you are hearing. And speakers are so very subjective. Are you able to get out and do any auditioning?

M3 or M5 Saphires

M3 or M5 Saphires

From a sheer musicality approach, you cannot step a foot wrong with the Stenheims. The A2 is in your range and will pretty much blow anything in its class away. If you’re pushing your budget, the A3 will likely be the last speakers you’ll ever buy. The Hegel will grip the hell out of the A2 and yet it’s probably a bit high on power output, they scale like nobody’s business. The halo graphic and stereo separation is mind blowing. Probably one of the most musical speakers in the world. You’ll not regret a single moment. 

First, if at all possible do NOT use the 15x15 room — it’s an absolute nightmare from a bass perspective (I know because I had that exact size room years ago). I heard Joseph Audio Pulsars (original version) with Hegel electronics and the sound was sublime. Not too warm, not too cool, just sounded like music with outstanding imaging/soundstage, and they’d work well in your room. Just one option, and best of luck.