Streaming transport recommendations

Hope you're all enjoying your music while keeping safe. 

I have an integrated amp, complete with a DAC module. I need a streamer without one. Sound is my top priority, functionality second. Bills an whistles not so much.

When I say sound I'm mainly looking for sound stage first, then clarity and separation and all the rest.

Any recommendations up to £4K (ish) welcome. I would consider pre-loved within that budget as well.

Amp Aavik U-150 with DAC
NAD M50/M52 combo (this is retiring, hence the recommendation request) 
Very revealing 2.1 speakers
No subs

Thanks in advance.