would this computer be any good for WoW?

Yes.

1. The AMD Phenom II x4 955 is a great viable processor. If the bios isn't locked then you'll be able to overclock it, furthermore boosting your performance..

2. The HD 6790 is equivalent to the GTX 550 Ti (a bit better, actually) and is a good low-mid range graphics card.

Overall, you will run the game on high-ultra for 60+ FPS. (All ultra, but you might have to keep shadows down). Maybe even all ultra. My GTX 460 (AMD equivalent HD 6850) + AMD Phenom II x4 955 runs it ultra 60+FPS.

it`s ok, but I would prefer an nvidia video card and intel processor

Yeah its more than enough to run WoW. 4gb Ram good enough for WoW and by the looks of it this computer looks like its made for playing games.