Jason, The short answer is that no, you don't.
When you lift weights, you don't actually gain any muscle. In fact, you lose muscle when you lift weights. During the periods of rest between lifting weights is when you actually gain muscle.
The theory behind doing cardio after weights is that you need the explosive energy in your muscles to do a proper weight workout and that if you do your cardio prior to weights, you won't get a good weight workout. The reverse isn't as true - you can do a cardio workout without the explosive energy that a weigt workout requires. So go ahead and do the weights then do the cardio and force your body to use up the fat stores during the cardio.