Yep, SRO is the only way to go for Spelling Bee. It's also a small theater with no balcony overhanging so the view and sound are just as good as in the seats.
I got there at 11:30 on a Friday and there was still SRO available.
"Valtava, iso pullean hurmaava HITTI." New York Post (as quoted by Hairspray, Finnish Regional Production.)