It seems there is a big gap between the cheapo Barska stuff and the Aimpoints, Eotech, etc.. Vortex has a couple of options. Looked at the Vortex strikefire and found the dot to be too big/fuzzy for longer shots. The Vortex Sparc may be a good option.
Eotech is running a $60 rebate until the end of the month. Grabagun has the 512.a65 for $369 so $309 after rebate. A little over your stated range but it's great sight. The 65 moa ring gets you on target fast, 1moa dot is crisp and precise for longer shots, takes plain old AA batteries. It's the one I ended up with and am happy so far.