Was trolling around on GunBroker and decided to go with a 300 pistol upper from PMA.
http://www.pmarmory.com/ar15-upper-assembly-s/1851.htm
Went with a 10.5 inch barrel with a 1/7 twist.
Returned very happy from the range yesterday as my new upper and pistol lower from Rock River matched up perfectly.
Price was not steep, and after 100 rounds or so I had no failure to feeds/eject.
I did not purchase a new bolt or charging handle, so it helped with price.
I'm researching loading data now, but I primarily ran subsonic ammunition on her first outing.
Pretty happy camper right now.