You have a LOT of great options for that budget and have gotten some good advice here.
I’ve had a lot of speakers and amps over the past 6 or so years, mostly moderately priced used gear. I’m always looking, for resale, and the ones I like stay around for a while.
Speakers make the most difference in the sound quality. Listening to the smaller systems in an office a bit smaller than your space. Favorite bookshelf that come to mind:
B&W 601 S2, Quad 22L, Tannoy Sensys, KEF Q1, Monitor Silver 5i (older small floorstanders), Elac B6.2, and currently Klipsch RB-5 which will likely stay permanently. All are in the $200-350 price range.
NAD and Yamaha and some Denon are favorite amps. I have a Yamaha streamer now with my main system. Looking for a Bluesound to replace it. You can also get vintage like a Pioneer SX-750 or low wattage Marantz. I'd stay with newer for speakers though.
I wouldn’t spend a quarter of my budget on cables. I did get the Canare mentioned above for my B&W Matrix 804 because they recommend bi-wiring. I think there is a slight improvement, but certainly not dramatic m(y listening area and positioning aren’t ideal.)