I’d wait for gen 13 chips and hope to get a better deal on a gen 12.
If you go lastest gen Nvidia it’d be rtx 30xx. I’d consider 3060ti as they’re smaller or a 3070ti but they’re a lot longer. Ti cards have more CUDA cores than non Ti cards.
Keep it simple and you’ll be happy.
- Get a good air cooler, I’d look at Noctua. I’ve always used the D15 but they are big, the NH-U12A is worth a look. The NF-A12x25 fans are super quiet and move a lot of air.
- I’d use an nvme drive for the system, roon server and hqplayer.
- A separate internal hdd for audio. I’d stay away from NAS. Keep the audio file drive in the host machine.
- Hardwire the server. (Avoid WiFi at all costs)
- Get a mini PC with a x5-Z8350 and use one of jussi’s images to use as an naa for the dac. I have a crappy no name mini PC from amazon that allows boot from a micro ssd card… it works but it doesn’t like the newer naa images so I’m using v4112 but it works.
So much for simple. Lol 
I use the Microsoft’s Remote Desktop app on the iPad that I use for a roon remote to access the host machine if I need to change hqplayer settings.