My middle of the pack Samsung (1 year old) has a very nice picture, but not when there is a lot of motion. Then it has significant pixellation. I think this will depend on the model you purchase and is not indicative of all Samsung products. However, my Sony has very little pixellation.
You will need a sound system because the speakers on the Samsung are pretty bad. My Sony has very good sound, but even so I use a surround sound system on all my TVs. The Samsung tuner is quite good and outperforms the Sony in picking up over the air broadcast TV. My antenna uses a Motorola amplifier, which helps with all my systems.
I don’t usually heat the gym where I keep the Samsung and it is below 60 some nights and it is not a problem.