With your set up and quality of your gear, I’d spend on a good steamer with an app you like, then I’d pair it with a DAC. As others have recommended, buying used is the way to go. In the digital chain everything will matter, especially with your gear. Upgrading which you will likely want to do is a lot easier if you go with a stand alone streamer and DAC.
I’ve had all in one streamer / DAC’s and separates. If you go the all in one route, Lumin D2 with upgraded power supply is really tough to beat. If you go the separate route, Aurilac and Lumin both make great streamers with apps that are well supported. Don’t sleep on how important that app, interface is with a streamer. Node, Cambridge have probably the best in BluOS. MHDT DAC’s are amazing, had the Pagoda balanced but also depends on what sounds good to you. MHDT is very musical, can make even bad recording sound good but they aren’t detailed or as analytical as say a Weis DAC. Research different DAC’s, different designs and implementations, why people either like or dislike the sound signature, roll with what fits best for what you like and the synergy with your existing gear. Then pick a streamer paying close attention to what outputs on the streamer maximize performance and what inputs on the DAC maximize the performance of the DAC. Synergy is key and both streamer and DAC’s will have options, streamers outputs and DAC’s input’s but you’ll find most of the gear will be designed with one of those maximizing sound quality, performance. Buy used, then if you get the itch to go a different direction, you won’t lose too much $$ and the DAC is what you’d swap out. I’ve 2-4 DAC’s that I have been able to a/b compare on my system for a decent stretch, in my system, you can definitely hear the difference from DAC to DAC.
Good luck and welcome to the streaming journey.