Keep your Shimanos until you can buy something lighter, more aero and with wider internal rim width. I just spent $1,300 on some Reynolds wheels that were money well spent. They're light, stiff, aero and pretty affordable for a carbon rim. Yes there was a speed gain but it was marginal with the wheels and tires. Maybe .2 to .4 mph. Not small but it's not life changing. Stick with your Shimanos for now.