Are my speakers good enough?

Rack?

5 tier Fraim - cherry wood 

Cables ?

And dedicated mains albeit only 2 un switched Crabtree sockets 

Do they sound good? Yes? Then yes.

Your system is good enough for a 300, that might up your opinion of your speakers a bit. 

CDI, I have pretty much the same system as you and, although our speakers are different, I have pretty much the same dilemma - 555 or speaker upgrade next? I am just about to demo a 555DR in place of my ahem, a.n.other XPS and will let you know my findings. I take Chris's point too and realise a 300DR might also be a sensible next step.

I also have a similar system (NDX in place of the NDS) I did upgrade from a Hi Line interconnect and NAC A5 speaker cables to S/L cables this was a major improvement. Earlier this year I changed the 250dr to a 300dr and without doubt this is the best value for money upgrade I have ever made the 300dr is something special, grip and control is simply awesome its like having a free speaker upgrade well worth a demo just got to save up for the S/L  interconnects.

I think if you've got the itch about your speakers you're going to have to scratch it with some home demos.  I'd vote Focal Sopra 1s but they probably don't fit your placement criterion.

555 and 300. My speakers sound way better with non DR 300 than they do with 250DR amp

In my experience speakers either work in a room or don't and better gear cannot greatly improve that factor. Speakers that work well in a room will show improvement with better gear. Speakers that aren't working won't benefit from electronic bandages. That said, acoustic room treatment can be a boon to a given speaker's performance.

Would it be worth a demo of the “natural” upgrade to Kudos S20? That would let you keep same house sound (if you like it) and hear how much the same design but max spec’d drivers and x-over components really add to the mix... As others have said, questing for info to know whether a move is worth it is a useful thing to do to satisfy your curiosity ...

(Disclosure: I have S10’s in what is likely a speaker-heavy system, driven by SuperUniti now traded in awaiting Nova on my return from a work assignment in New Year... your source electronics seem well above this level, so look to the upgrade that appeals to you emotionally, which seems to be speakers before boxes or cables!)

Regards alan

Upgrading to the S20 would give a significant improvement for not too much money, particularly if they can be found ex dem. The 555 is the logical thing to go for, either before or after the speakers. It worked wonders on my 272 and is really what the NDS needs to achieve its potential. 

The S20's are better than C20's, more controlled and refined.  I made the change a year ago, not driven by a requirement to upgrade but by a change in wood colour due to a furniture change in our sitting room.

I wouldn't say it was a wow change but a 'slow burner' noticeable over over a few days rather than minutes.  If you like the C20's then in my opinion you can slot the S20's in without any cause for concern as to needing to change positioning or issues with speaker vs room.  Superficially they are very similar to each other.

I suspect you will see more of an improvement than I did as your system is quite a bit further up the food chain than mine (NDX/282/HicapDR/250DR).

As HH has said, a 555 is also beckoning, if it were me I would be looking out for nice used examples of either and get whatever comes first, you may find you can do both!

Richard

S20s are a big step up from C20s and are not room fussy.  

Kudos S20 s/h -- check out Signals... 

I second WInky's position; do you like the sound you are getting? If yes, then you have answered your own question. If no, then home demos are the way to find out.

I will always recommend you look at some ProAcs with Naim gear if you are going to do demos; Response D2s if stand-mount, or something in the D18-D28/D30 (depending on new or used) range for floor-standers.