I also do a LOT of Photoshop and Illustrator. Also Adobe Premiere, and in the near future I will be doing animations and will be doing some computer codes..
yep you need more RAM, for today usage, i5 is still pretty fast for vga card, if you dont need top of the line, you can take mid range card.
660Ti is good, but if possible take 2 gig memory it would help if you run high resolution, effect or like that
so you can add ram, replace your stock cooler, add some fans maybe to give your rig enough fresh air