Detroit vs ARB. Is your rig a daily driver or driven on the street a lot? If so I would not install a Detroit in the front axle. I've seen people to do in trail rigs but usually not street rigs. I have an ARB in mine and I have no complaints, it just simply works. Just remember you will need to budget for an air compressor too. ARB makes a cheap one that runs lockers only for around 170 and EVO makes a nice bracket that has three mounting posts so it doesn't vibrate like many others. It is around 50.
Axles. I have RCVs and love how smooth they are and I don't worry about breaking a u joint. That said, they are very expensive and a good set of chromo shafts with full circle clips is plenty. If you are on a budget I would skip on the RCVs. I got them because I upgraded to the 35 spline RCVs and ARB.
Ball joints: this is where I shoot myself every time I think about it. Back when I ordered my PR I had a new set of Synergy ball joints sitting in my garage. I decided to pass on the ProSteers since I already had a set. The Synergy ones are definitely better than stock but they still wear out pretty quickly. I can already start to feel the slop and it's been about 6 months. I'm running 3.5" bs wheels and heavy Toyo 37s so it puts a lot of stress on the ball joints. My next set will be ProSteers and I wish I had done it the first time. You figure at 100 off you are in them for about just over 2 sets of Synergy joints. With the pain in the ass it is to change them well worth it. If you are on a budget and have to pick between the ProSteers and say RCVs, get the ProSteers in my opinion. You could always upgrade axles later down road, that is much easier than changing ball joints every year!
It's all about budget and what's best parts to get on that budget. Hell if we all had unlimited budgets we would all probably be running PR60s up front and 80s in the rear but that mortgage bill keeps coming every month
Just my 2c, take it or leave it.