Cherry and pecan is a great blend for beef, and for that matter chicken and pork. Smoke over low temps and then sear. Or run the smoker hot and do it in one step. Best smoker for doing the low temp them sear is the Mini-WSM.
You can smoke burgers on a charcoal grill. You don't need a smoker. Just sear the burgers on both sides then throw some hickory in the coals and close the lid. Make sure the top and bottom vents are completely open. Let them cook until desired doneness.