The wife and I have a great 1080i Vizio 32" monitor that we got at Costco right before we dumped our membership (How can you shop at costco when you live on a boat? I can't get 100 rolls of TP down the companionway hatch!) It was like $575. We don't have the 5.1 system though. On our Catalina, we just didn't want to run all the wiring for rear speakers, but there are those who would find it no problem. We did lead the stereo outs to a pair of great Bose speakers that were originally used for a computer. They are small and efficient and can blow us out of the boat when we crank it up!
We love the setup. We have our setee constantly in the down position so it is just a giant couch and the screen is on the Starboard wall. Everyone gets to watch movies in the evening while we are on the dock, which so far is always. I know that when we cruise we won't have the TV and I bet the kids don't know that yet, but that is why you go cruising, to get away. The rest of the time though we have a great entertainment center. Some of the newer flat screens work great so just look for the best of what you can afford.