Listen to your coach. 105 grade bikes are usually spec'd with basic, utility grade wheel sets. I was a doubter until I upgraded an early Trek Carbon 105 grade bike I had with an expensive, lighter wheel set, but noticed an immediate difference in average speed. Bike accelerated, quicker, and was more responsive. Almost like getting a new bike. Even if you're not interested in speed, it still means less work over the course of a long day. Was well worth spending the money to do it. I think it's the most effective way to improve performance on a typical 105 class bike.