Wearing less clothes makes a lot of difference. I don't mean go out riding in public bollock naked, I mean ride in shorts and tee shirt, also comfortable and flexible footwear helps to make you feel more agile.
I've been through the light weigh bike stage and got no benefit at all, the bike creaked and crunched a lot meaning I spent more time fixing it than I did riding it.
ATM I'm riding a 9.6kg stock and I'm riding it incredibly well compared to any of my other bikes which proves the weight isn't everything.
But at the end of the day I'm not here to tell you how to spend your money, if you can afford to do it, then why not?