• Factor in all the additional costs.  It is much more than just the real estate costs.  What does it mean in lost time for your people?  How will it affect your time?  What added communication costs will you incur?
• What departments would you move?  What departments do they interface with?  How will that be affected?  What impact will that have on performance?  Is there another department you could move that would not be so dramatically affected?
• How will the move affect your execution?  What is likely to not get down or take more time to do?  What will you have to do to counteract this?
• What if you were to break your lease early and move to a larger space?  How would that benefit you?  How would that compare against the additional real estate and moving costs? 
• If it still makes sense to open up a second office in town, even after factoring in all the additional costs, what can you do to counterbalance the negative side effects?  How will you keep people in touch and on the same page?  How will you make sure that things get done that need to be done?

A second location may still be the right move.  Think ahead about what you are getting into.   Otherwise, it could cost you dearly.  People could take much longer to do things.  You could end up executing poorly and performing poorly.  Plan ahead so it does not end up that way.