I would never buy a $4000 set of wheels and tires or a $3000 exhaust, so my vote is for the supercharger. I do have a $1200 set of Apex ARC8, an $800 quad resonated Top Speed x-pipe, $200 used MS pulley, $65 K&N filter, Vishnu tune with meth injection, $200 used H&R springs with shortened guide tubes and E36M3 bump stops, $100 Stoptech Street brake pads and $100 braided brake lines.
I'd rather have a VT550 than what I have, but it was not an option for me. People are moving on more frequently these days and parting their mods. You can get some good deals if you are patient.
I agree that a tune and pulley would be mostly wasted if you later bought the supercharger that comes with a different tune and does not use an underdrive pulley. The tune is nontransferable, but the pulley could be sold used.
From what you write about your intended use, I'd recommend the VT550 now and maybe save other changes for later. Plenty of people run ESS kits on cars with stock suspensions and brakes, although I agree that for serious track use, at least better brake pads would be needed.