The LN32D550 you linked has great reviews everywhere and also appears to have excellent gaming performance.
How significant is input lag to you? It doesn't bother most gamers. If you play competitive shooters or rhythm games you won't want to settle for anything with high input lag though. I ended up gaming on a 10 year old CRT screen because I couldn't accept the ~30ms input lag on my toshiba HDTV! I would make fast response/low input lag the top priority in your search since you plan on using it mostly as a gaming display.