George raises perhaps the best point about RRS gear- The resale value here & on fleabay is practical full retail. You just can't get hurt badly, even if you decide to go a different direction later.
As far as ballheads, I need a new one, and am personally leaning towards the Markins.
I also want to look further into the brand-new Gitzo heads. They look VERY promising.
I've been using their BH-25 with quick release plate on my Gitzo 1541T for travel this summer and the combo has been great. Very lightweight, yet sturdy.
You won't go wrong with RRS or for that matter Kirk. I'm using two RRS L-brackets and a Kirk L-bracket. The Kirk is fully compatible with the RRS lever clamp, so no problems there. In addition to the L-brackets and lever clamp, I'm using a lot of other RRS gear, but opted for the Markins M10 ballhead.
RRS is great stuff and a fine company to do business with. I have bought several L brackets in the past two years, the finish is excellent and the fit precise. I am waiting arrival of a BH-40 and an L bracket for my D700 tomorrow.