Re: need help with waders!
If I were you, I'd just rent, providing you're only going to use them a couple of days. They rent for about $20 a day. September weather is generally pretty nice, but it can be unpredicatable too. The high country will start seeing snow in Sept. so be prepared for that possiblity. A good pair of waders is going to cost you in the neighborhood of $200 and up. Or, you can get neoprene waders at Wal Mart for about $50 then another $30 for wading boots. They also have breathable cheapies for about $80 then the boots seperately at $30.
If you rent you can take advantage of the local fly shop's expertise on all the info you'll need to have sucess and of course supply you with the best flies for your adventure. You can do that without the rentals but you'll feel better about picking their brains if you shed a little cash to help out the local economy.
As far as booted or stocking foot, stocking foot gives you the better options for the type of socks you're going to be wearing depending on how the boot style fit your feet and body. And you can just get a better fit on seperate boots.
Oh, yeah, chest waders for sure and felt soles.
Enjoy your trip to Colorado, and catch some big-uns.