Thanks for the reply! I've done some searching on EN13537 found those european sites. I also came across this thread, which speaks to the same points I asked about:

http://www.backpacking.net/forum/ubbthreads.php?ubb=showflat&Number=172301

My biggest unknown to me is still the alpine side of things. I agree a true 20 degree bag that has room for layers (like the alpinlite) will work fine for midwest shoulder seasons into the mid teens. I have no experience for what temperature to expect in spring/fall alpine situations. I've found people talking about using everything from 30 degree to 0 degree bags.