BlobbyBlobFish

I'm in a bit of a pickle, and I need help. So I wanted to build a pc that could play modern titles for as cheap as possible (My first rig btw). So I went and got a MSI Armor rx570 4gb, a 450W power supply, and a Dell Optiplex 7010 for the build. But then the Dell Optiplex was cancelled, so I went and got an HP Compaq Pro 6300 MT because the specs were similar. Turns out that the HP may not have been a good idea. The power supply is weird, and the card may not even fit. I need guidance. Pls Edit: I didn't quite flesh out the situation I was in well enough, so let me make it more clear. During the day this is posted, the items have not arrived yet (Sorry for not saying that before). The graphics card and power supply was planned, but the Compaq wasn't. I did very little research before purchasing, so I had no idea that the Compaq's motherboard could interfere with the card due to some tall looking capacitors in the way. By the time I found out, the item was already in transit, making it uncanclable. I say this all with some uncertainty, as I don't know if the parts would interfere with the board at all. I just need some expertise, as I am very inexperienced. Btw, I am totally down with janky solutions like dual power supplies. I just don't want to spend extra if I don't have to.