Your 8 cubic foot tank will hold about 60 US gallons in total so figure a rather large stocking when it has been fully cycled. As always, stocking is done in stages as the filter is ready to accept that level. The cardinals, rams and DGs is not an overstock situation in a tank that size, even with the cories added in, but pay attention to the advice from onidrase. Although you will have lots of water volume, there are fish that are suitable for a typical 55 gallon tank, that measures 4 feet long, that would not work in your shorter tank. An example that comes to mind is swordtails or zebras. Swordtails and zebras are energetic swimmers that use lots of room. The tiny space of 2 feet would be inadequate for them even though I keep some swordtails in a 29 gallon tank. The length of a 29 is more than your mere 2 feet and gives them more swimming room.