My bike, which has a triple chain ring, came with mostly 105 components but the front derailleur was Tiagra. I had lots of problems with it and was always bringing it to the shop for adjustments. One day while they were adjusting it, it broke. The only derailleur they had in stock to replace it was an Ultegra, so they put that on my bike and now it shifts great. So, it might be easier/cheaper to just upgrade the derailleur instead of switching to a compact/double.