If you're near a Fry's Electronics, they may have the Q9540 for $269 (retail box). I picked up one last week. Today they have the Q9400 w/cheapo ECS mobo for $249.
I bought the Q9450 and it's a decent overclocker. Can't get over 450 FSB though (tried 2 procs and P45 and P35). Supposedly someone got the Q9400 to 4.0.
Under $300, I'd think they're all right for the price. I bought my Q6600 when it was that much. If this will be your first quad then consider the Q6600, they're around $175 now.