I don't know if this helps, but here's my experience.
I have and use the lower end 484RC2 and 486 RC2 Bogens, and although they do a respectable job, their lack of a tension control while released didn't cut it when I started using heavier lenses (which was pretty much right away). They also droop significantly and inconsistently when locking, and are frustrating to position precisely with a long lens.
Let me mention that I have a few reasonably good tripods, though my shooting style dictates that I don't use them that often. I tend to like versatility, and have a Uni Loc System 1700, a Benbo Tracker I, a Bausch and Lomb Advanced Titanium for a very lightweight full sized pod, and a very small and light Velbon Ultra Maxi for travel and light digicam use. All but the Velbon were found on Ebay at ridiculously low prices -- the Uni Loc was the most expensive @ $112 USD.
Back to the ball heads. The models that you mentioned are all superb, with the Markins and the RRS leading the pack, AFAIC. Add some Arca Swiss blocks, and the prices get very high very quickly. Used ones, even on Ebay, don't sell for significantly less -- and I watched for quite a while. Unfortunately, the most viable alternatives that met my criteria aren't that much less expensive. I finally narrowed it down to the Acratech Ultimate and the Bogen 648MG RC2. I was leaning towards the Acratech, but won an auction for the Bogen for $175. There aren't too many of either of these offered for auction without a significant reserve, so I got lucky.
The RC2 QR is not really up to the task for reasonably heavy lenses like a 300/2.8 (over 5 lbs for the lens alone), but my Tamron SP 300/2.8 and the DS balance well on the tripod ring mount, and I really don't have any trouble using it. I would, however, NEVER carry the camera mounted on the tripod any distance more than a couple of feet to adjust an angle. I use a Camdapter grip strap on all my cameras and ALWAYS dismount the camera before I walk with it so it's always secure.
The RC2 will also not be of any use if you want to mount a Wimberly or Jobu gimbal mounts -- they all use the Arca Swiss clamp. The problems with the A-S system for me are the block cost, the fact that I was already pretty invested in the RC2 system, and I was used to and pretty satisfied with it, even given its significant limitations. There are, however, some reasonable looking and relatively inexpensive gimbals available coming out of India that I'm looking at since I really doubt that I'll be using anything substantially heavier than what I already have. These don't need an A-S block. If I decide to get one, it'll probably be a bit later this summer. The Bogen gimbal is also a lower cost alternative that has a lot of fans -- it's not as elegant as a Wimberly or Jobu, but it works. even with very heavy lenses.
Both the Acratech Ultimate and the 648MG RC2 are light -- less than a lb. Both are adjustable for unlocked tension, but the Bogen is easier to adjust. Both have great build quality with the Acratech getting the nod for quality finish and smoothness. The Acratech is undoubtably cooler looking. The Bogen is much easier physically to lock and unlock due to its hydraulic mechanism. The A-S clamp is definitely superior, but the RC2 system is a lot less expensive and faster -- at least for me.
The 648MG RC2 is about perfect for me. Compared to the Acratech, it's a tad less smooth and not nearly as cool looking, and would be tougher to clean if that became a factor (which it hasn't). Even with a pretty heavy lens/cam combo, position can be easily adjusted, unlocked tension is easily set with the micro-click resetable tension adjustment knob, and the hydraulic locking mechanism is very easy to set with just a touch and locks absolutely solid.
Let me say that I think you're on the right track considering the higher end tripods and heads and trying to consider future needs for your current purchase. I hope that I've added a little insight and information from my thoughts on these models.
BTW, those Giottos legs were on my short list before I lucked into the Uni Loc. It was a little to massive at the leg joint, so I was leaning towards the bent bolt designs anyway. The similar Gitzo was just too expensive. I later picked up the Benbo really cheap from another auction that I couldn't pass up and it serves a purpose. It's lighter and just as versatile, but not nearly as well made nor as solid.