need help for pick the GPU, i used to had issue with my RX580 GPU PASSTHROUGH

I am been think about to come back to Unraid, because it is really powerful. i tried it 2 year before, i like it but i do have some issue with the GPU pass through, and i wasn't have good enough time to learning it from scratch, so i quite and back to bare metal Windows OS. 

Because i have the RX580 GPU, and that seems like the issue which cause me not properly pass-through my graphic, therefore i want to buy a budget GPU(around $400 or lower), but i am worry about it would cause me the same problem 

hence, my question is : what would be the prefect GPU that i could easily passthrough without much problem. my last experience was horrible. i am new to this.

here is what i have already :

motherboard:

ASUS ROG Strix B450-F Gaming Motherboard (ATX) AMD Ryzen 2 AM4 DDR4 DP HDMI M.2 USB 3.1 Gen2 B450

CPU: 

AMD Ryzen 5 2600 Processor with Wraith Stealth Cooler - YD2600BBAFBOX

RAM:

32G

SSD: 

1TB

HDD:

2TB

8TB

1TB

I expect to use it as my work station, 

and i use windows(VM) as my daily device

i don't play games that much currently. 

please help me and give some suggesting/ selection, tell me what else i will need to do in order to accomplish that. 

and based on my situation, i have RX580  already, if i brought another GPU, do i still be able to use my old card? or it would become useless.

i do not know if i could have 2 graphic card in the same tower, if yes then what is the point to have them both. 

thanks a lot, i am really looking forward to see any replies.