I got lots of experience with a ton of different machines... if this is your first sled and you're new to real backcountry mountain riding the RX1 will make you hate sledding. They are extremely heavy!!! and being new you will spend alot of time digging it out and lifting that sucker... and trust me your riding buddies will not enjoy helping you move than anchor either. With a turbo they make enough power, but get it stuck and its still a pain in the ass.
The skidoo 800 motor is problem prone, there is plenty of evidence related to that, same with the 800rmk bottom ends.
If you're goin used, find a clean Arctic cat 1m king cat, they are cheap and plentiful especially down in WA. you can score an 05 for 3500-4500 and the 900 twins are a very reliable and solid motor. They go great in the deep for an older chassis. You will find it much easier to progress than on the Rx1