Honestly if all you're watching is sports, the TV speakers are probably fine. I'm usually yelling at the TV too loud due to Bama's constant eff-ups the sound is lost on me anyway...
If you also enjoy movies, then it'll depend on your set-up. If it's two-channel music oriented, it's not great regardless of the quality of the gear (need a center channel for dialogue). I really enjoy movies, especially those with a compelling music element, so went deep on integrating high-end multichannel into my music system once upon a time and spent a small fortune but in the end switched to a simple standalone option for the TV (center sound bar, sub and two small rears).
I found it better to keep my two-channel system separate and optimized for music - YMMV.
Room size will play a big role in the TV size. For 65" and above, you need some distance from the screen for the best experience. Lots of calculators online.