Thomas - mine is 160mm inc the solid feet. Do remember the venting is done via the top and I think you should allow a good 50mm ++ for this, noting it has a fan too although mine rarely, if ever, has come on.
i am very curious to read your feedback when you will have the 500. I feel the 500 is too much for such speakers, but it’s just my feeling.
I don’t want to spoil your pleasure however. What is your room size?
Perhaps, like me, you can’t accommodate bigger speakers?
I have Apertura altra, french speakers, around 6k as yours.
Yes I have Fraim and double height (Tall as listed) uprights to accommodate the 500. I think the gap is ~95mm from the top of the 500 to the above shelf. This is (obviously) due to the design of the Fraim not a specific need for the 500. I’m not sure if a 500 can be used with a Medium Height Fraim shelf - recognising you are using the glass shelves at the moment? The measurements on the Naim 'site suggest a 500 can be used with a Medium height upright as the available height for use = 180mm.
The manual only indicates that the top & bottom vents shouldn’t be blocked e.g. by carpeted flooring. You may be OK with only 25mm gap above but the more is the better in my view.
Definitely in my view get the speaker right first. If you can! If the abscissa is the right speaker for the OP and his room then getting the amplification optimum makes sense. For that large size room I would have thought JMR’s next model up might possibly be better without losing the middle and top character that’s the OP likes, however he is the only one that can decide.
The Abscissae have about the same total bass driver area as my PMCs, the same 4ohm impedance, and the same sensitivity. I find if I want to play mine spiritedly they will happily take 500W (or more) on peakson that basis the 500 might well be an appropriate amp. (It’s what I would want to try if I ever did get round to hearing Naim power amps: the trouble is with tri-amping it is three times a lot of money! Very possibly 300s on middle and top would be quite adequate.)
Put the 552 on the vacant top shelf, remove the shelf it was on and it will fit in your rack where the 300 is now but get help putting it in there, I nearly gave myself a hernia trying to feed the head unit into the gap I’d prepared for it in my Fraim.
You only “use” half the room, presumably in terms of the distance between you and the speakers (as do I in a slightly larger one), but the speakers interact with the whole room. Unless you hear them you won’t know whether the Orpheus would have adverse effects - they would only interact more with the room if you played them louder, or if they have greater bass extension. Greater bass extension is good in my book provided any resonances are controlled: however only you know how you like it, and there are always other considerations.
I heard the orfeos in a much smaller room than yours. They were doing fine.
Having said that , i would listen to magicos and atc actives , if you are looking for cost effective ways of improving your system. You probably don’t need a nap 500 for the abscisses.
The ATCs piqued indeed my curiosity. They seem to be fine speakers, in particular their active versions.
The NAP500 will, obviously, do nice job driving the Abscisse. Which also leaves me with a large number of options in terms of potential speaker’s choice.
it’s not only a question of more bass. You can get more details, bigger soundstage, better separation of instruments, more body, nicer tones…
My speakers have 2X 17 cm . I am in the limit in my medium room of 19/20 m2. The Orpheo are 2 X 18 cm , not a big difference, and your room is 38m2, and treated.
I have already heard some JMR and also Atc. For me the JMR are more refined and richer in textures. ( i heard only atc 40 and 19 a).