I have an assortment of 50 and 56mm scopes. They are great but the game changer now is lens coatings and glass quality. The Swaro Z5 ($1,200 ish) 44mms I have used the past couple of years are fantastic. They very well could be "better" in low light than my older 50 and 56mm Leupolds, Swaros, and Zeiss. My point is, look at the top brands in your price range and you might find a 40-44mm has the quality you want without having to have a larger objective.
