Garmin is usually considered by most to be the better brand of the more common GPS units. They have many models at around $300 retail.
I am currently using a Lowrance iFinder, and I have been very pleased with it so far. The only thing I don't like is that I have one of the original models that was not waterproof. I use it mostly for four wheeling, and even under heavy foilage I find that I can maintain a good satellite lock on my position. It's WAAS enabled, so it is also very accurate.
I have tried Magellan a long time ago because it was cheap. After trying for 10 minutes to try and get a lock on my position, I almost threw it out on the highway. Instead, I returned it, got my money back and never bought a Magellan again. The newer models may be better, but since my experience with Lowrance is so good, I haven't bothered to give Magellan another chance.