Solo 5

I used to have Bose Solo 5 for my PC and it was quite adequate. Just make sure the soundbar you're getting has analog input (3.5mm or RCA) because digital inputs tend to have latency, which is not good for gaming.

Bose Solo I've bought refurbished for around 150 USD

I know this might be a tired question here but I didn't find a conclusive response right now. 500€ is definitely my upper limit, for reasons. The last soundbar I owned was a Bose Solo, which was better than the TV speakers but obviously not all that great. At first I thought about the Sonos Beam 2 however I heard from a friend that his tends to act up because the app sucks. Then I thought about one of the Bose Smart Soundbars, there's one on sale rn for 320€ I've also seen people recommend the Samsung Q600C or the Polk Signa S4. Of those options, which one is the best option? Mainly for watching movies and gaming.

The days of TVs with great picture AND great sound are over. That said, every soundbar I have had is a huge improvement over my TV, so I'm perplexed by your results. I've always had a soundbar with subwoofer or a soundbar with sun and rear surrounds. The sound is fantastic. But even the little Bose Solo bar we have under our 19" kitchen TV sounds waaay better than the TV alone