Normally I'd say the tank is overstocked. Can you calculate how many inches of fish that is? If it is more than 80" I wouldn't suggest any more fish unless you'd be willing to get rid of some of the livebearers. Are the fish healthy with no signs of stress? Since livebearers really don't have a significant effect on the bioload of the tank due to the fact that they are small fish and don't produce much waste, I'd say you're ok so far. However, angels do produce more waste and need more space. (General rule is 10 gallons per angel). If you removed say 3 of each guppies, platies and mollies, you could trade them in for 2-3 juvie angels. If you like them a lot, you could trade in some more livebearers for a couple more. I would not suggest adding angels with what you have now. Ideally a 46 gallon tank should have no more than about 20-25 fish. If you are very attached to your livebearers and refuse to give them up, I don't blame you. If you are really committed to getting angels, however, then that is the sacrifice you must make (well, that or buy another tank). Whatever you choose, good luck. Angels are great fish.