I have a set of old Shimano m076. They are used- bought it from a friend. the inner sides of the shoes each have a hole in them caused by rubbing with the crank arms.

I am thinking of replacing the shoe for a number of reasons

1. Planning to race this season and think I could do with more stiffness. (The m076 have no carbon sole)
2. The rubber thread of the m076 is so worn out, it no longer grips on the surface because the cleat sticking out is thicker than the thread itself. When I clip into my XTR Race pedals, the thread does not rest on the platform of the pedals and all my weight lies on the cleat-pedal interface.
3. The shoe isnt very tight fitting on my feet and I infer this as my shoes being a size too big.

I dont know if I should spend my money on a pair of new Sidi Dragon 2 Carbon SRS/ Mavic Fury, or use it to lighten up my bike.

I ride a singlespeed, by the way, if that affects anything