I've flown JFK-AMM and ORD-AMM a few times in Crown Class. My experience has been that the on-board service is fine and the seats are very roomy. The seat pitch is around 83 inches - old style seats that recline to 180 degrees. The only bad part about the seats is that there is no shell for privacy. I'd recommend 3C - it's in the center so you won't have to step over your neighbor to get to the aisle. Food on RJ is really quite good and nicely presented - trolleys are pushed down the aisle and they plate whatever you choose. The video system needs a good deal of improvement, but you'll probably want to sleep from JFK to AMM anyway since it departs late evening from JFK.

RJ doesn't have a lot of A340s and they are really worked. My experience has been that departure times from the US are almost never met -- a few months ago my flight from ORD was delayed 7 hours because the flight was late from AMM (I think the aircraft actually started in Bangkok!).

Overall, RJ provides a very nice service at a reasonable cost. Enjoy Crown Class but just don't expect SQ or BA FIRST.