Solid list for $750! However, for $10 more you can grab an RX 7600 or Intel Arc B580 which offers AV1 hardware encoding and newer driver branch support. Also, if you can stretch another $25, jumping to AM5 (Ryzen 5 7500F / 7600 + DDR5) will give you a massive upgrade path through 2027.

How are the temps on the NH-D15 G2 with the 9900X? Did you need any fan curves tweaking?

What FCLK are you running? 2000MHz 1:1 with DDR5-6000 CL30 seems to be the golden ratio for AM5 latency (~61ns in AIDA64). Anything higher than 2133MHz FCLK caused memory controller instability.

Insane specs! Which power supply did you end up using for the 5090? Make sure you have at least a 1000W ATX 3.1 unit with native 12V-2×6 cable to handle high transient power spikes safely.