only reason i upgraded anything on my bike was for comfort and fit.

fizik saddle
fizik post (for better support of carbon rails)
easton 90 bars (swapped from those 70s lbs gave me)

elite bottle holders (since i read good reviews)

wheels are something else i want to be upgrading but something within budget, stiff/light/reliable, good all around wheels...that includes entire built wheel with hubs/spokes...not sure i want to do custom wheels...