How long is your commute, and how long have you been doing it? If you're just getting back into riding a bike after a long period off the saddle, you may just be in a transition period where your butt and legs are getting used to the saddle again. For my 10-mile (each way) commute, I wear cotton boxers under cotton shorts - probably the worst thing you could possibly wear according to many cyclists - and I have no problems with soreness or chafing. I save my technical gear for long rides. Just saying that you might want to give it time before spending a lot of $$$ on cycling gear.