There's opinions out there that if you're already in there, you need to do extended lines and longer links and this and that and the other. Most of those guys are doing some serious wheeling, so when they start hitting full droop some of those things do become a necessity.
If you're going for a light wheeling rig, or even just want the lift because it looks good, you should be fine with nothing extra. Your brake lines might be a little tight, but they should be ok. Your end links might sit at a bit of angle, but that's not going to hurt anything, aside from wearing bushings faster. I do like the idea of the diff drop, as axles aren't cheap, but that comes in the kit you mentioned I believe.