I'd add +1 for the 757. However it's not the easiest aircraft to fly. But if you want an aircraft with complete FMS and very well simulated systems, then this one comes very close. My favourite tube-liner for X-Plane. However it's the 1980s version so it doesn't have a GPS - it updates the IRS positions automatically only from nearby DMEs during cruise. You need to have on mind that you must check the IRS precision before planning RNAV approach or let it couple of minutes to fix the alignment especially on very short hops.
The CRJ comes with somewhat limited FMC but it flies OK and it has one of the best manuals I've seen - that's also a very good bet. However many other addons are better value for your money and the documentation regarding to an aircraft performance is rather insufficient. FJS 732 is something I like to recommend to people who are beginners to jets. No complex and confusing avionics - if you look on captain's panel, there's very little you don't know from Cessna. And it has the most funny livery I've ever seen! http://forums.x-plane.org/index.php?app ... file=26775
. Before buying the JAR A320 be sure to check if you are able to deal with the fact that you can't use a keyboard to put values to a FMC 
.Almost every aircraft can be used with X-FMC. I had some difficulties setting the holding or changing the destination for diversion. I recently bought ifms and it looks like it doesn't have those issues. When using X-FMC I always have a GPS as a backup in case I screw it up (which is not hard).
