You do not want surround sound outside.
Before going any further, you are probably going to get a bunch of responses about the evils of watching television outside, and then the other camp about noise pollution. Just a warning, so get some thick skin real quick.
Soundbar.... yes ... good alternative. We started using soundbars on all our televisions. We have one in the camper and it also has the bass woofer. When we crank the volume, the entire trailer rumbles!
I haven't tried it outside yet, but if you can eliminate the bass, it should work very well.
Just remember, you want the volume loud enough you can hear it. But if you can hear it in your neighbor's campsite, it's too loud... thus the reason for no surround sound!
Most soundbars have a surround sound setting. Somehow it projects the sound and bounces off the walls and sounds like something came from over there, and then something else sounded like it came from over here. It's really quite interesting how it works. But if outside, there won't be anything for the sound to bounce off of, except the neighbor's camper, and this just isn't a good thing.
We have a Boise, and 2 different LG's. We like the Boise the best, but it's also the most expensive!