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You do not mention how much you may want to use the tripod and ball head for things other than the new 300 f2.8 lens, and that could enter in to what you should get. My largest lens also happens to be the 300 f 2.8, and I really enjoy it.
The Gitzo GT35xxxS series of tripod legs with the removable plate top are very nice, and I can highly recomend them for that size of lens. You should avoid a center column tripod for a lens of this size. For a ball head, I use a Really Right Stuff BH-55 ball head, which is a low profile head design. The 300 f2.8 mounted on the BH-55 using a lens plate on the lens works fairly well for hand aiming, and when locked down is nice and stable.
If you want to follow action at all, some form of Gimbal mount is important. The Wimberley SideKick works well with this size of lens, and the BH-55 has a good pan base to provide smooth movement. I use my Sidekick on some trips where I do not want to haul along the full Wimberley. If you want to shoot action for long periods of time with a big lens, the full Wimberley, or a similar high quality full gimbal mount, is really a pleasure to use.
I suggest you look over the above items, which are a good match to the 300 f2.8, and then decide if you want to invest that much in a tripod system. You may have the resources to go that way soon, but if not you might be able to get part of it and make due with other parts until you can build up the full setup. The classic bad way to get to a good tripod is to buy smaller lower quality stuff, and then need to get rid of it all to eventually buy the right thing. If you can manage it, buy the right things now. If not, you at least know what to aim for eventually.