Again, you dont need much to run those programs, just a lot of ram and hard drive space. My 10 year old dell desktop PC with onboard video can run PS VERY fast.
You dont need anything overkill like the core i7 for your needs... that processor is more for video editing when rendering a video which takes a long time. You dont need a lot of processing power for photoshop though.
The difference between hard drive speeds are only noticeable when you are moving large files from one place to another... you will also notice a very small difference when opening up programs such as PS and Illustrator too.
What I strongly suggest is getting at least 4GB of DDR3 ram which is included in the cheapest version.
If I were you I'd just buy the least expensive version which might I add has very good specs, with an intel core i3 processor, 4GB of DDR3 ram, and a 320GB HDD which is more than enough space for just using those 3 programs.
If you can just find the $799 version refurbished!