It's ok, skip the LSD until you'll have the money, anyway it's applicable for track-like roads
About the brakes, get the mod done first and then depending on money left and necessity you make your choice. For that kind of power increase you could get away with only new pads and a pair of drilled to the front.
The exhaust is a big issue for me too, don't make the same mistake I did, whichever you choose ask about the noise levels first. I think that Supersprint has a quiet and a louder version. If you get the mods at Autodelta ask Jano I'm sure he can help you with that, he's a kind fellow...
About the tires, I take it you 're asking about the standard 2L size, I'm sorry I don't know, I had 17" since I got the car, so I have experience about bigger tires (215/45/17), but search the forum I'm sure you'll find something.