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I'd definitely do some trial and error there. Renting (or borrowing) before you buy would definitely be recommended. If you're discussing lenses like that, and you're not sure which one you want/need, you definitely need more hands-on familiarity and experience. All the 70-200 f/2.8 type lenses are quite heavy, and with the hood attached, quite long. Practical is not a word that comes to mind. You will look like a serious photographer using one, and depending on what you're shooting, that may or may not be how you'd like to be perceived. If you're doing posed people shots, sports, wildlife, etc it would likely be fine. For casual people pics, street shooting, or travel, a 70-200 f/2.8 is extreme overkill in my mind, not practical for those uses, and likely to get worse reactions from your human subjects. The 24-70 is a great lens. It will be great on DX, and great on FX. I don't use it myself, because I prefer the focal length versatility and VR of the 24-120 F/4 VR for what I do primarily. If I mostly shot more people-oriented photos, the 24-70 would probably be my go-to lens, despite it's size and length relative to other FX midrange lenses. Also, 24mm is quite a wide angle lens, and it's entirely possible that you might not ever really need anything wider (considering that the point of a wide angle lens is perspective, not "getting everything in")/ Again, the size of the lens and massive hood would probably not be ideal for street shooting or other more causal shooting where people might react to you with "why so serious?" Also, I would contemplate how much you really NEED FX. Thom Hogan's website (bythom.com) is a great resource for Nikon shooters, and he has a number of articles that are excellent for really making you properly evaluate your gear choices and their relevance to your shooting. FX, while having many great attributes, has many drawbacks. The lenses are bigger, heavier, and more expensive. The camera bodies are bigger, heavier, and more expensive. While you can get a shallower DOF, getting sufficiently deep DOF can be a problem on many shots. Primarily though, look at the weight/size/cost of a good DX system (say D7000 / Tokina 11-16 f2.8/ Sigma 17-50 f/2.8 OS / Sigma 50-150 f/2.8 OS) and compare that to a similar FX system (say D3s / 14-24 f2.8 / 24-70 f2.8 / 70-200 f2.8 VR2). The difference is staggering. Seriously contemplate how those factors would effect your use of your camera system. I only deal with FX because of what I shoot, and how I shoot. For what I do, the dynamic range of the D700 (in it's time), and the DR and resolution of the D800 now, are paramount to crafting my images to the levels I demand. I'll eat the cost, and deal with the weight/size, even when it's time to lug that weight/size up 7,000ft of mountain and back down in one day. But many others might not feel the same way, and be as uncompromising on image quality. For some, the convenience or cost might be worth a small sacrifice in image quality, or that sacrifice might not even be present/relevant for their specific uses.