If your line is old it wouldn't help your casting. Inspect it for cracks, if so it needs to go in the bin. If not try a fly line cleaner, a clean line will make a big difference.
Most expensive rods cast well however you can find cheaper rods that will cast just as good. I would look for something with a life time warranty.. I think Black Shadows fly rods do and they cast okay. I am sure there are quite a few on the market these days. A good tackle shop should let you have a cast before you buy. I hope that helps.