I lived with a Leben CS 600 for many years, first with ProAc Tablettes and then with Devore O93s. Before getting the Devores, I tried the Leben with ProAc D2s (a lauded combination at the time).
Obviously, I preferred the Devores over the ProAcs. But rather than simply assert “O93 roolz”: the first thing I would say is that the Leben is not a “tubey” tube amp — it’s not rounded, dark, “caramel” etc; in fact, it’s quite lit up. I think Prof observes the ProAc house sound very well — I would certainly not describe it as analytical, and those coming from e.g. B&W are likely to describe it as “musical”. But it is also quite lit up. If your priorities are soundstaging, detail, and picking out musical lines, then you will like it. For me, with the Leben, the ProAcs were too much, and the combination lacked things I value greatly: tone color, texture, and body. The Devores, by contrast, major in those areas; others might find them lacking in soundstaging and other “hi fi” characteristics. (The Devore X gives you more of the latter at the expense of some richness and body.)
I hope that helps. Of course, the usual comments about room, sources, and ancillary components apply. (I think A23 cables are at least a compulsory audition to hear the Os as they were designed, for example.)