generally if the kit fits the needs of the project, it's your best bet to just get the kit. if, for instance, you are doing a complete rewiring + case modding for managment + adding new fans and UV lights ect ect you are probably going to be doing it again at some point, so spending extra on supplies now will mean having them later when you want them again. last time i lapped a cooler i ended up spending $25 on sand paper, when the amount i needed was only worth about $8. i ended up using the rest of it to sand off the paint on my armor full tower's back panel for a complete repainting, and using some of the rough grit i still had for sanding off the edges of holes i cut with dremels and drills for other case modding projects. i still have about half the paper i bought left, including a whole tone of 1500 grit which is great for touching up the base of your cooler if you remount it and it gets a bit knicked in the process.
ed: this goes for other things like case fans and what not as well. always buy one extra than what you expect to use since you will always find a use for them later, or in case one of the fans goes bad sooner than the others do. i learned this one the hard way, when my a64's stock cooler died, and the cooler could have come with a spare fan for a buck extra. they didnt make them anymore and i ended up going and getting a Vendetta2 and lapping it instead. now im hooked on comp modding as a hobby and i'm putting out money i dont absolutely need to to make my comp glow in the dark!