Amp and Preamp recommendations for Yamaha NS5000


Currently have SOTM 200 ultra -> denafrips terminator +dsp board -> Audio gd he9 pre amp -> dual bryston 4bsst -> NS5000.
I am loving the sound... just sounds incredible. But wonder about amp and pre amp upgrades down the road. Any thoughts on what might work well? These speakers are 87 db efficient.
So far thinking all pass labs amps + pre.

Ok with buying used. Would like to keep things under $20k if I can. Thanks.
smodtactical
So the 250.8 just sold. So gotta look at other options.

Thinking of the coda no.8 also. Also the accuphase e470 or p450
After a lot of research I am leaning towards either a Pass integrated or a 150.8 or 250.8 with my audio gd he9 preamp.
Or a luxman m900u or 509X.
A friend of mine recently listened to the NS5000 with a VTL tube pre, m5000 power amp and brikmann dac and said it sounded too smooth. I know the ns5000 is very neutral... do you think pass or luxman might be too warm overall? HE9 is likely neutral to slightly bright so may balance things but I do have a denafrips terminator so that may also push things to too warm?
Has Ayre been eliminated?
I would have thought an AX-5 Twenty would split the difference nicely.
From an amp perspective, a Chord Ultima 5 could be interesting for you.  300w into 8ohms.  The amp is less clinical than prior Chord amps.  Pretty darn neutral.  The error correction tech makes it pretty special and these are a really special line of amps.  I have a customer who has one for a pair of Monitor Audio Platinums.  
Pricing is just about right paired with a variety of tube preamps.  I am planning on getting an Ultima 6 Later this year to pair with two different preamps, the Art Audio Conductor and the KR P-135.  The nice thing is, you have flexibility with both units in terms of rolling.  I hear amazing things about the P-135, ironically with EML Mesh 45s.  The Art Audio runs 12BH7s and 6922s so there are plenty of NOS options.  
You could obviously use a variety of other preamps, VTL, PS Audio BHK, McIntosh c22, etc... and get a great result.  If you want a more energetic sound, a SS preamp will deliver that or you could go direct from a Chord DAC.  
I know you are in Canada.  Normally I would say I am happy to take all your gear on trade but am thinking the border may make life difficult.  No problem for the ARt Audio or KR gear, but a trade and Chord sale could be tough.  
Guys thanks for the suggestions:
@twoleftears Actually a local dealer does have an AX-5 twenty used for sale for about $5600 usd. I definitely am considering it. But kinda leaning towards going for a power amp so I am open to a future pre-amp upgrade.
@verdant Chord amps seem interesting. I don't know how easy it would be to get one up here in Canada. Heard chord is kinda a pain to deal with also.