Yes you made the right decision to go with the Panasonic.
The RP-56 has a superb picture and very good sound. I recently had a discussion with a reviewer who lives in my neck of the woods and he told me that it measures more accurately than any of the Sonys that he has tested (for video, of course) and even better than the more expensive Panasonic he reveiwed that has DVD Audio. He believes that the Sonys have some extra processing/emphasis in the chips that cannot be turned off. To some, however, the extra processing gives the picture more punch, but at the expense of accuracy. He also told me the reason why the Panasonic is better is because there is less processing and features in it. As for the sound you will have to be the judge, but at the very least you have an excellent dvd player.
Keep this in mind when you go shopping for speakers and amplication.
In the long run you will find as you get further into audio that often times, less is more; the fewer things you have in the circuit the more pure the sound is (it should be more reliable too). Most of the time efficient speakers have a very simple crossover or none at all and lower powered amps have less transistors or tubes and an overall simpler circuit design. Therefore, when you go looking for your next set of speakers consider its efficiency. This will allow you to use an amp with less power. Like the Panasonic keep it simple.