i actually replaced my clutch and springs about a month ago, i had some slippage going on pretty bad in the higher RPMs and gears. I went with the barnett kit. I, too, priced out the stock / OEM plates, discs and springs, but almost doubled the cost of the Barnett. the only difference i can tell is that the clutch lever pull is slightly tougher. you won't notice it in normal riding, but i have an unfortunate commute home now that the schools are back in session. So in traffic, you will feel it. MUCH smoother than what i was working with before though. i have very similar mods on my SP2 to those on your bike.
FYI, if you get a Barnett kit, make sure you get the one for the SP2 because they have differing parts than the one for the SP1 (judder spring, etc..)