The $20K Soulution Audio 330 Integrated Amp is a Bargain ?

Would 509X be a better choice for less money?

I've heard plenty of good things about the 509X. Only you can say whether it would suit your needs and the needs of the rest of your system and budget

I would think the Analog Domain plays more in the realms of a C/M900u combination. The following review offers a good perspective

https://www.hifi-advice.com/blog/review/analog-reviews/amplifier-reviews/analog-domain-m75d-and-m75p/

I've not heard the 330 so couldn't say how that'd compare

@highend666 Soulution gear is pretty damn good.  Better t9 get it discounted.  I have the 540 SACD player / Dac. Very HAPPY.  Excellent source.  My reference was the resonessence Mirus pro signature dac. I got the player below 10k which you rarely see. But I’m set as a source for life I run it through using my Melco music server. I’m in a great place 

What i call a bargain is a used Gryphon Diablo 300 for 7.5k

Boulder integrated and vinny rossi comes to mind. Solution is very very nice..up to the listener.