I would definitely recommend purchasing at least Photoshop. I've always stayed far away from costly subscriptions if I can. I don't have extended, and I don't know if it's of much use. I also have Lightroom, I think there's some feature overlap there, but LR in itself is really awesome.
One huge difference between earlier versions of Photoshop and cs5 and 6 is 64bit support. I went from cs2 to cs5, and the difference in file handling between the two versions was night and day. Of course this was comparing 150Mb many layered files, so it depends on the kind of photo editing you use. I didn't find a whole lot of practical difference in Illustrator versions, but image tracing works really great. I don't remember it from cs2, I didn't use it much then. Acrobat and indesign conversion features are vastly improved.
jm2c
Andy