well any of the three you said are amazing cards. I would say the 4770 over then GTX 250 but if you can get a 260 that is another story.
There is 2 versions of the 260 though. There is old one that first came out then there is the remake which has a different name depending on which company your getting it from. The EVGA one is called the GTX 260 Core 216 which is more powerful by a fair bit as it has a nice jump instream processors and texture units.
I am not to familiar with Autocad but with 3dsmax you would see the most improvement with rendering and you will see good photoshop results as well.
As for dx11 and Windows 7. If you are okay with your current step up for another 2-3 months I would say hold off but if you need something soon I would just say go for the 260 with 216sp and you won't be let down. If you think you will really want dx11 but still need something now then get the cheapest card now (likely the 4770 depending on where you live but the 250 is about the same as well) and then that will last you until the price drops on the new dx11 cards about 4 months after there release.
will the dirextx 11 cards initally be that much better than the current dx10 cards? i may borrow a card off of work/a friend if i can till w7 comes to fruitation, will nvidia and ati release cards in the run up to it?
Has anyone gotten a breath of the possible specs of the dx11 cards?
I don't think they will be that much better right off the back however their release will drive down the price of the current cards. There is no release date on them (as that would affect the sells of current cards) but that should be out in the next 3-4 months tops. Some hint that AIT will have theirs out by the end of next month but it's all just here say.
There are to many rumors about specs but they are allover the place are barely match from one list to the next from what I have seen.
They will be 40nm so they should have some good clock speeds and overclock very well.