I went streight from advanced recreational diving to CCR. Got the nitrox cirt in order to dive CCR and barely used it before starting my CCR class. One trip to honduras and i was simultaniously convinced of the benefits of nitrox and even more so of it's limits on OC. i think of nitrox as a gateway gas, as soon as I got using it I begin truly feeling the advantages of cutting nitrogen out of the mix and soon after realized how much more valuable it would be to be able to adjust the mix to match my depth. I quickly began to experience what a pain it is to be limited by MOD of a fixed mix/variable po2 and exhaling so much of that o2 out with each breathe. I quickly came to see the advantages of constant po2 diving, no MOD's, hours worth of volume in much smaller bottles, drastically excellerated off gassing on ascent with a nifty nitrox blender able to make the perfect mix for every depth, on the fly. I lug 13 cf tanks around now, not 80's. doubles were not a possibility for me as my back was beginning to give me some serious grief...at 35 my lumbar discs were showing signs of wear.
I used to get really tired, cold and achy diving OC air, more so than most of my buddies. now I can do a 2 hour dive and still feel pretty energized without the aches and pains.
My advice: go streight to CCR ASAP, IMHO, if you know you will be diving enough to make it worth while...it's not for everyone. it will take some time before you will likely feel ready to really take it deep. I'd suggest getting lots of hours in up front doing some relatively simple dives and gradually extending your limits and training.
I got a good deal on a credit transfer between cards, baught it on one card and swapped it over for very low APR and paid it off in a year...a hundred plus hours into it and I still don't feel as confident as I did on OC.
Also, I would recommend not getting too caught up in trying to figure out what the perfect rebreather is, better to assume your first one won't be your last. It takes getting some experience to really begin to shape your preferences. Buying used, starting out on mCCR are viable options. there are some serious advantages to manual control if you don't really need a set point controller. rebreathers keep their value and you can always resell and get a different one down the lines...that's what i've done.
my first one was a full eCCR, my second one is a somewhat tricked out mCCR and was on the work bench the day I bought it. I had come to want a configuration that no one offered as stock so I modified it with different electronics, rewiring the head from day one (with a fair amount of guidence, mind you). there is no way i would have been comfortable doing that the first time around and no way I would have known what suited my needs until I got 100 hours under my belt.
take some time, decide if you are going mCCR or eCCR and then learn as much as you reasonably can about the various ones available and then just take the plunge with one and go have fun!
hope that helps!