I think the RR product is good for the money. The BPE's don't fit 97+ XJs well but a little grinding gets them in just fine. The shackles are the best on the market (I think); they are very strong. If you have any ability to modify things and half a brain this kit is easy to install and shouldn't need any support. A stock exhaust shouldn't hit but many aftermarket exhausts do hit. You don't always need longer U-bolts but you should buy new ones anyway because they stretch and aren't meant to be reused. You don't always need longer center pins but if yours are rusted they will break.
Guys it is a BUDGET Boost. For $110 what do you want?! If you wanted to do it right you wouldn't be cheap and get a BB!
BTW, to the second post, pre 97 XJs have a screw in bump stop, no need to grind. It doesn't look screw in but I promise you it is. Use some heat, PB, and large channel lock pliars and it will come out. It is a tight fit on all XJ but some silicon spray and a rubbet mallet gets it in there and it won't slide out when you are offroad. A plus in my book.
Buy a longer rear brake line. It should be an option on any lift kit. It may be long enough with a 2" BB sitting on the ground but any articulation will max it out, and I'm positive you don't want your rear axle dangling but a rubber (or any material) brake line.