So I just bought a Hegel H390 and

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what speakers under $10.000 sounded the best.

+1 @hilde45 — there’s no way for us to know what might sound “best” to you, which is really the only thing that matters. You really need to share what sound characteristics you’re looking for and are most important to you to make any kind of a meaningful recommendation.

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.