If FEL, I would say go with at least the 4wd units, or the X500 series.
I have had two 445's and now have an X485. I like the extra power of the X but many features of the 445 are missing. One important one is the excellent air intake system that filters the air before getting through the radiator and through the carburator. Deere took a step backward with the bolder one-piece hood arrangement and the stockier 'look'.
If I could trade even up for a 445 with similar hours, I would not hesitate to do it (but factor in a few other things such as equipment and that even trade becomes more difficult too).
They are cadilac machines, and expensive initially. But they keep their trade-in value as you probably have already found out. So the initial investment is good, IMO. They are work horses, and I haven't regretted moving up to that 400 series, one bit. /forums/images/graemlins/wink.gif
Basically, the 445 and the X485 are the same, but the X585 is 4wd.