A decent leg set & head can add another thousand or so to your budget, but once purchased, you will reap the benefits & you will not regret it.
The next should be the height at maximum leg extension. If the model you are considering has a centre column, leave it down! An extended column will flex & introduce vibration. Some tripods have a flat top plate which the head fixes straight onto. This is my preferred method. Remember that a head will add around 4-6 inches to the max height quoted in the manufacturer’s specifications. Also, does it allow the legs to splay out for low level shooting? How low will it go?
A decent ball head, such as the Kirk BH-1 & sidekick, costs around the same as a full Wimberley.
Weight. This is very important to some people. Ideally what we all would like is a tripod & head that weighs less than 1kg, is tall enough for Martin Johnson to use without stooping & can carry a max load of 25kg. Forget it, it ain’t gonna happen! Go to the gym or get someone to carry it for you if you can’t handle it. But I suppose that if you are prepared to lug a 600 f4 around, a couple of extra kilos is not going to bother you.