It depends a great deal on what use you're going to get from it too.
I hung around forums that persuaded me years ago that to become a "proper" photographer I needed to use a tripod all the time and it had to be this that and the other. I spent over £600 on a manfrotto 441 carbon legset, Markins M10 head, etc.
I've used it a handful of times - I just don't want to use a tripod for the vast majority of photo work that I do. Of course it's useful occasionally, but wasn't worth spending what I did.
Additionally, the manfrotto 441 has a terrible design flaw, with the legs held to the top section by an expanding collar made from cast magnesium. One cracked under reasonable normal use (repaired under warranty, but very poor design, wrong choice of material for that use).
So, what I'd recommend...
Definitely get something that uses the Arca-swiss style dovetail clamp. There's now a good number of cheaper chinese made heads that do and these are perfectly adequate for most people most of the time. The Redsnapper RSH-12 is a good example of this:
http://www.redsnapperuk.com/camera-accessories/RSH-12_Ball_head.html
I wrote some thoughts about the RSH-12 here:
http://photo.net/filters-bags-tripods-accessories-forum/00V5Iv
Legs... well, it's a matter of budget, and of preference. 3 section or 4? Flip locks or twist locks? Carbon or Alu? One of the things that pushed me to the manfrotto 441 was a dislike of twist-locks (which came from trying to use a cheap garbage Cullmann tripod), so I limited myself to flip-lock legsets. In retrospect, having now used a few good twist-lock legs (my father has two Gitzos for example), I regret that decision. A good twist-lock is fine and actually probably better.
Ultimately as a very solid "budget" choice I'd go with this combo:
http://www.redsnapperuk.com/camera-accessories/RSF-284M___RSH-12_Ball_Head.html#nogo
If you want to spend more then there's any number of ways to do so. A lot of companies make very high-quality kit but like hifi you'll get into the realms of design philosophy (eg Acratech) and personalities (eg I won't buy anything from RRS because of their support for california's Prop 8).
Edit: Forgot to mention, within the Arca-swiss style system, there are specific camera plates, lens plates, lens foot replacements, etc. Some are very expensive (eg Kirk L-brackets run north of £150 each). There are perfectly good plates available on ebay, for example this one I've recently bought for my 5D3:
http://rover.ebay.com/rover/1/710-5...0001&campid=5338728743&icep_item=151620148039