Which component to upgrade 1st ?

Oh and let me throw another DAC suggestion into the mix…

Bricasti M3 or M1SE used are within your budget. Find these on a used market with a built in network player and you’re good to go as far as the DAC upgrade is concerned. 

The ML Vantage have a powered woofer. So the panel is pretty much the only thing that presents a challenge to the amp. However, I think you’re fine with the ARC amp driving the MLs. I had the ML Montis and used Rogue ST-100 tube amp mostly in triode mode which puts out about 60-65w/ch. I also used Pass XA-30.8 with the MLs and it rarely moved out of pure Class A operation.

Even though the Qutest is a great DAC, IMO upgrading the DAC will be the biggest impact in your system especially if you switch to running all XLRs with the ARC gear. The Weiss 501 DAC should be great and will replace both the Node and the Qutest.
I would then tackle the preamp next and would look into something like ARC Ref5/se. Stay with the ARC for your preamp for synergy, sonics and a piece of mind.

By the time you’re done with either or both upgrades, you’ll sit down for a listen one day and realize that your speakers are not on the level with the rest of your gear. 😀

You mentioned you like warm sound…may be look into Harbeths when you get around to the speakers.

@milo0812 not sure on dealers in your area. Sorry.
I would contact Bricasti with that question. 
In NJ I believe Verdantaudio may be a dealer for both Bricasti and Weiss. He also posts frequently and had a lengthy thread on shoot out between different DACs. 

@milo0812 don’t forget…look into running all XLRs with new DAC (assuming it’s got balanced out).