You could also go with two tents. For three season go with a tarptent, Lunar Duo, or other lightweight shelter. Then watch, REI Outlet, Sierra Trading Post, Campmor and other outlets for a 4 season (non mountaineering) tent for winter. For around your $500 budget, you'll get a very light tent with good ventilation for 3 season and a very sturdy, heavier tent you can close up tight for winter.
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If I wouldn't eat it at home, why would I want to eat it on the trail?