There are always cheaper answers.
Reshimmed diffs are a FRACTION of the price of LSD's, dont have the cluncking and noise problems either.
GTR diffs are also cheap 2 way upgrades.
You'll be surprised how much of an emprovement good brake fluid is as opposed to upgrading brakes. I Penrite SIN at like $22 a bottle its a Super DOT4 or DOT5 (not exactly sure, could check if your interested) and will dramatically stop brake fade and other common problems.
I try to be as big of a tight arse when i modify as possible. Ill search car yards, second hand parts, forums, e-bay, yahoo auctions everything before I finially decide where to buy what I want and in the end it always ends up a heap cheaper than the commonly asked prices..