Please Help Receiver purchase help - recommendation

[sard]

I have 2 Polk TSI 500 speakers, a polk sub PSW 505, polk center channel cs10. I need to buy an AV receiver, I have no idea what to buy. I only want to spend $200-300. I currently have an older pioneer receiver VSX 815. I feel like can get better sound out of my speakers and feel like i need to upgrade my receiver. I also have polk surround speakers. I only want a 5.1 system, i am not buying any more speakers

I know nothing about OHMs and don't care too. I just would like someone to tell me what to buy for my price range, the best deal for my buck

I am using this to watch movies, music is no big deal

Thanks for the help/advise in advance!