Looking for Advice on Upgrading My PC

Hey everyone! I recently realized that my computer needs an upgrade if I want to enjoy more games. Here are my current specs: - CPU: i7 6700 - GPU: RX 550 - RAM: 16 GB DDR4 - PSU: I think it's around 220-250W - SSD: 256 GB - Motherboard: HP805D I got this PC off Amazon for about $300, and I see now that it was probably not the best choice. It has a small form factor case, which complicates upgrades. I'm particularly interested in upgrading my GPU since it struggles with many games. However, to do that, I first need to upgrade the PSU. The new PSU won't fit in my current case, so I'll also need a new case. I have a few questions: 1. What GPU should I target that won't bottleneck my CPU? I was thinking about a used one like a 5600XT for around $100-150, just to plan for the future. 2. What PSU should I buy that would be compatible with that GPU? 3. Can anyone suggest a suitable case for about $100? I liked the CORSAIR 4000D Airflow Mid-Tower ATX Case, but it's currently out of stock. Thanks a lot for your help!