What would be an upgrade over the NAD M51 Direct Digital D/A Converter?


I am looking for some advice as to an upgrade over the NAD M51 DAC.  The objective would be to get my digital end to be more engaging so that there's less of a gap between it and my vinyl front end (Manley Chinook pre, Technics 1200 GAE).  

Would this necessarily require me to spend >$2k?  I'd be fine going used.  I have a Primaluna Dialogue HP integrated, so the replacement DAC doesn't need to have an independent volume control.  

128x128jbhiller
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You know you're right. It may be tough to beat this DAC without dropping a fortune. I may just need to realize that my analog front end is just better and my digital is very listenable just not going to be as good. 
Try a stand alone preamplifier. after trying the Auralic Taurus pre i couldnt go back to using the M51 as a preamplifier
I upgraded from an M51 to a PS Audio DirectStream DAC when it first became available and haven't looked back.
The DirectStream DAC does not use a conventional DAC chipset, instead uses an FPGA, so once or twice a year PS Audio makes firmware updates, once installed, improves the performance of the DAC, something that is not typically possible with a DAC with a conventional DAC chipset.
No plans to replace the DAC, from someone who tries stuff out and does lots of upgrades.
Added an Innuos ZenMini to the NAD M12 Analog/Digital/Streaming Preamp which is based on the M51. 

It got very close to the PSA DirecStream / Auralic Vega G2 that i also was demoing. 

My conclusion was that, what ever DAC/Preamp i end up getting i need to have an Innuos as source. Just a question of which. I have tried various combinations with the following products  Lumin T2 , Auralic Vega G2, Pirmare PRE35 Prisma, NAD M12 w. BluOS, PSA DirectStream w. Bridge II, Cambridge Audio Edge NQ, PSA Stellar Gain Cell, Simaudio Moon 390.