As Kal, John and TJ advise, the 50 times per inch of aperture is only a theoretical maximum. In practice I work with only 30 times per inch for most seeing and have only gone as far as 150 x.
There will only be 2 or 3 days of the year where the sky and atmosphere might allow the seeing conditions to approach the theoretical limit the scope. As Steve suggests, the best view often isn't with the highest magnification, as there often isn't enough light to blow up the image, a bit like pixellation when zooming in on JPEGs.
I suspect that you share the common expectation to see planets in their full pin sharp, image enhanced, punchy colour glory of Hubble type images we see in magazines. There is no way you will be able to get postcard views of planets just using your eyes.
One factor often overlooked when determining the limits of seeing conditions is the limitations within the human eye itself. The Fovea part of the retina contains mainly Cones in the central part and Rods in the outer part. Cones give you colour vision during daytime, whereas Rods allow you to see black and white at night. That's why you often have to use averted vision at night to see dim faint objects in your peripheral vision, to get the light from the faint object to hit your Rods. At night your cones might as well have gone down the beach, since they need lots of light to determine colours, so in effect you are almost blind to colours and rely on your rods for black and white vision instead. So now you know why colours look faint at night, as we are mainly daytime creatures, well some of us are.
