As others have said, the driver is the most difficult club to hit. Can't explain why you are able to hit the Wal-mart driver so well. May have to do with the different type of shaft and flex on the shaft. What loft angle is the Sumo 2 and what kind of shaft does it have?
Anyways, your iron play will determine how well you play every other club. Why? Because I believe the fundamentals are taught through iron play. Fundamentals such as properly addressing the ball, stance, posture, ball position, and swing plane. In addition, your irons are going to get you on the green, not the driver, or the woods, or the hybrids. On a moderately distanced par 4, you can get away with playing your irons and still play a decent round of golf.
Personally, I don't have the success you have with the driver. I can't hit is straight nor can I hit it consistently. I have now focused on mastering my irons before I even lay an eye on the driver. After irons, I will focus on the fairway woods/hybrids, and then finally the driver. IMO, the driver will be a bonus. If I can hit the irons, woods, and hybrids straight and consistent, I won't need a driver ;)