What GPU's are enough for 4K gaming (specifically for emulation and pc exclusives)?

There aren't much PC exclusives I am interested and the ones I am interested are pretty much indie and strategy games which don't require a powerful system.

But I want to build myself a PC specifically for Retro games (sixth gen and before specifically + Wii U/3DS)

I want to build myself a poweful but not much expensive PC because I know I won't be using that PC much outside of this. I have a 4K TV and I will use my TV to play games and I use upscaling, hd texture packs if possible, shaders that require powerful PC specs basically.

So what would you recommend for a GPU and CPU to choose for this usage? I want the upcoming RTX 5090 and my budget says otherwise lol and I don't want to waste my money for something that won't be worth it. I use my Playstation for trophy system alone to play games so I won't play AAA games even though it would give me infinitly better graphics than even PS5 Pro could offer....