Thoughts on lens kit (NIKON WARNING)

[Xebadir]

I know how many people ask about these things, but atm I am looking for my goal lens (The lens that motivates me to finish a section of my PhD).

I am currently looking to add to my kit....the question that springs to mind is with what (Why is below...so you will understand...but we all know I am just looking for an excuse.

On the one hand I currently have my D300, a 50 1.8, a 10-20 4-5.6 and a 70-300VR, but one of the things I am considering atm is where to go to fill in the annoying gap that I have (you know, the only where you are always wishing for that little bit more or less).

I am really enjoying taking portraits, so something thats fast and shoots with a decent bokeh would probably be the go. I really like the 50mm (its fantastic, nifty all the way), but I often yearn for that gap between 20 and 50 to get the shot that I want (also that speed out wide is also something I am looking for). At some stage in the future I will probably go to full frame with the D300 as my backup, and I am wondering whether I should be looking to this when purchasing my long term lens investments. There is also the potential of being asked to shoot a friends wedding unofficially.

Some of the ideas I have had:
A 24mm 1.4G, 85mm 1.8D with the existing lenses, so on full frame we are talking the 24, 50, 85 and the 70-300, eventually probably the 70-200 would be added.
A 28-70 F2.8, 85 1.8D plus the existing.
A 24-70 F2.8 and leave it at that (IE I could stretch to this lens, but in doing so that probably knocks my camera spending off for a year or so).
A 17-55 F2.8 DX and an 85 F1.8 and forget about FX for a while/upgrade when necessary.

So at this stage it pretty much comes down to:
85 1.8D alone. I like the idea of the 85 as its a bit more petite than the bulky 70-300 but still gives that bit more length to the shot....the 50 has got me sort of hooked on using primes....I guess its being spoiled by the speed and forcing to rethink the shot to deal with the focal limitation.
28-70 F2.8 and 85 1.8D
24-70 F2.8
17-55 F2.8 DX (CROP LIMITED for the Canonites) and 85 1.8D...this sort of sprung to mind because I dont really notice that gap between the 50 and 70-300 unless I have to change for portrait, and in that case I could use the 85.

Any input or laughing at my overthinking of the topic would be appreciated. And if you think something completely different to those mentioned I would appreciate your thoughts.