Choosing new speakers for Naim Nait 5si mainly for hip-hop, RnB and jazz/soul

When you say “the vocals come from the ground and I want them to be airy, coming from a higher place and going towards the ceiling” Shahinians spring to mind. Whether a 5si would drive something like a pair of Compass I don’t know. 

There is one pair of speakers that immediately jumps to mind and that I think you would like.  Focal Aria 926.  I would say that they are capable  of delivering all the things you mention, but.....the potential problem is the Nait 5si.  Although 5si meets the minimum recommended power output, I've believe that the 926 can be a difficult load in real world use, and I get the impression you would intend to drive them pretty loud.  Why mention them then?  Well, if there is a Focal dealer nearby, they'll be able to advise better on how the amplifier would cope, and hopefully know far more about it than I do.  It might be fine, particularly if you're looking to upgrade electronics in the not too distant future, and you would have speakers that I have no doubt will reveal the changes you make.

B&W 683 S2 floorstanders.

Have you tried repositioning the Omens?  The tweeter isn't positioned that differently than in many floorstanders - perhaps something like a bit less toe-in (are they toed in?) would fix that particular issue?

If you're looking for "slam" in your hip-hop music, you're going to run into the physics problem that the 5si just doesn't put out enough current for many speakers to do that.  Have you thought about a subwoofer?  I've had a JL sub for quite a while, and reasonably positioned and reasonably set up, it can provide what you're looking for AND integrate well into the sound stage.

[@mention:40424794201076322] , I've heard Focal Speakers with Naim a while ago and they were good but missed the bass punch I want, however they were cheaper model than Aria 926. After them I've heard Monitor Audio Bronze 6 - they sounded fuller and with better bass for my taste however missed some of the details and airy highs. 

@BART, I've tried a lot of things. They are toed in very lighlty. The tweeter for the high frequencies above 10khz is positioned below the full-range driver and is at approximately 75 cm from the floor while at my listening position my ears at around 95 cm. I angle the speakers a bit up by adjusting the legs and this helps a bit but still the vocals seem very low. About the subwoofer - that's true, but I mainly miss punch and slam from the higher bass/low midd frequencies - like 150-200 hz. And a subwoofer hardly will give me that range. The Omens get really low and sometimes it seems like you have a subwoofer but they seem not to hit hard on this low midd freqeuncies and that's what I'm missing. 

I’d stick with the speakers and get a more powerful amplifier, such as a Supernait 2. A bigger amp will make it sound like your speakers are bigger as well. 

Despite the OP using a 5si, I doubt amplifier power is limiting here. Zu speakers are renowned for their efficiency and are big with tube users. The Zu Omen are are rated at 98-dB into 12-ohms.

No doubt the beefier SN2 will deliver more slam, but this would likely have as much or more to do with the speed and quality of the pre than the pure power of the amp. 

If you have them on spikes, you should raise up the front a touch so they point ever so slightly up. Having them both equally slightly raked back will give more air and height to the presentation and boost perception of bass  (This could be tricky - get a fine spirit level).  Easy job done.