Comparing available Dell Video Cards

Hello

I'm purchasing a new system and need help in figuring out what Video card would fit my needs.

The new system will be Windows 7 with Intel® Core i7-920 processor (8MB L3 Cache, 2.66GHz)

Use of system where I will be concerned with Graphics performance will be:
--- 80% - Photo editing - using PaintShopPro/Adobe PhotoShop
--- 15% - Panorama stitching (but want good performance when I do this)
--- 05% - 3D Panorama rendoring


In another thread on this site I came across someone putting various Video Cards in a comparison ordering
which was a great presentation of the information

Unfortunately the model numbers in that comparison had almost no over-lap with the cards I'm seeing offered
from Dell in the US or in the Alien-ware line. The model numbers were close but different.

Question 1 - What order would you display the following cards to show increasing performance?

These cards are most of those being offered by Dell for their high end models in the US. Some are offered in the Alien-ware line

ATI Radeon HD 5770 1GB GDDR5
ATI Radeon HD 5870 1GB GDDR5
ATI Radeon HD 5970 2GB GDDR5
nVidia GeForce 310 512M GDDR3
nVidia GeForce GTS 240 1GB
nVidia GeForce GTX 260 1.8GB
nVidia GeForce GTX 295 1.8GB

Question 2 - Of the above cards which would give be sufficent to meet my expected needs? I don't want to spend
money for little gain but may spend it if real peformance could be had. I certainly don't want to underpower
my configuration.


Question 3 - What kind of improved performance should one expect as one increases the on board memory of the video card?
For example, zero on board, 512M, 1Gig, 2Gig.

I'm trying to figure out if more ram necessarily gives a porportional jump in performance for the price. Again, the answer should be in
context with what my expected useage is.