How much do you have to spend?

OP, looking at your system your primary concern should be upgrading to a capable amplifier. Weak link first.

@parkergetdean +100

@fritzenheimer , in all seriousness, the problem with the NAD M33 (if it is V1) is that you cannot avoid its internal DAC, which is quite mediocre, (but better than its streamer). If you don’t stream or otherwise use digital sources, and want to stay with the convenience of Class D amplification, check out @hilde45 ‘s recent thread on Class D amplifiers. https://forum.audiogon.com/discussions/expanding-the-class-d-conversation-how-would-you-characterize-their-di

On the other hand, if you are using the M33’s streaming capabilities, there are so many better options for not much money.  This thread https://forum.audiogon.com/discussions/is-there-a-better-all-in-one-streamer-dac-integrated-amp-under-usd-5k

Has a lot of really good info on integrated amps that have good built in streamers and DACS. 

Wondering whether putting out another $10k would result in significant audible improvements…

A definite YES! 10k would likely help most of us.

+1 amplifier is weak link, maybe DAC the next

@fritzenheimer

For half the price of the Reference 1 Metas you can have the R7 Meta floorstanders. I went there from LS50’s and it’s a definite upgrade. Not sure but I think the price difference reflects where they’re made. The R7’s are first rate although it looks like they may not have the cool silver ones anymore.