You can commute on any bike. You can also commutify your existing bike at a fraction of the price a new bike would cost.

1. If your bike has a suspension seatpost I would swap it out for a non suspension one
2. I would look to get some good flat resistant tires like panaracer t-servs or Schwalbe marathons
3. I would look into adding bar ends to get more hand positions

I don't think you need to get another wheelset unless you are having problems with your existing ones. I don't think there would be anything wrong with getting another bike if you have the money. Plus it is always nice to have a backup. If you are riding mostly hilly areas for 8 miles then a roadbike would probably suit you better.