So you've got your boots and pack covered.
**Advice I took from guys on this sight.
Frog Toggs will do in a pinch. They are sort of like a poncho - maybe better. You'll survive a sudden rain/hailstorm. But you can't hunt in the rain while wearing either. The rain gear question is a big one and it depends on where and when you're going and mostly it depends on your tolerance for suckiness. I won't carry a true rain suit because I hate carrying the extra weight and I can tolerate being wet for a while. Everybody is different.
** I have a heavy duty rain set that I considered but simply refuse to carry the weight and I couldn't hunt in that either. I'm beginning to think I need to just drop a little coin on a set I saw at Cabela's. Not the best I'm sure, but will pack down in a little bag and is supposed to be fairly decent at repelling water. Wasn't nearly as loud as Frog Toggs and was camo. Like you, I can function a little wet so I hate to break the bank on rain gear.
Early September in CO should most likely just have brief sudden storms - nothing like what you're used to in GA. Typically early in September in CO a storm will be really windy and rainy for 30 minutes and then the sun comes back out. So for a day hunt when rain is not likely you can make do with Frog Toggs or a poncho (military surplus works great). If the forecast is for rain then of course wear a rain suit, which you probably already have.