I suggest a used RTX 3090 FE on ebay/FB Market which you can find for ~$500. Trust me, you'll want the 24GB of VRAM for SDXL because running a SDXL model, SDXL Refiner, SDXL Lora and SDXL Textual Inversion (sometimes a controlnet(img2img)) in ComfyUi will eat around 15GB of VRAM. Also, since they're next gen cards, there will be zero SD compatibility issues. Also make sure your PC has at least 32GB of RAM and run Stable Diffusion on a M.2 Gen 4x4 drive. Lastly, if you watch FB Market close you can come across a early RTX 3090 for low as $300 if you're fast, and the best part is you can quickly run a stress test on the card before buying.
Happy hunting.
FF12 Environment Library By Valhalla - Go From ~10ish Built-in FFENVs To 327 FFENVs! mediafire.com/folder/5mof7pqxvs0fr/FFENV
Current Rig: AMD TR 3970X 32C|64T 4.5GHz CPU - Nvidia 24GB RTX 3090 GPU -128GB Ram And Two 4TB M.2s.