My time has come!

Guys, i just got my taxes back and is time to search for my first mac. I do a little bit of Gaming (WoW) i've been away for the game for almost a year, but planing to go back for a bit. Im also a music producer, and im learning about video edit and all that, i dont do 3d stuff, so far too complicated for me.
I have a powerful pc that can do anything i want but im planning to give it to my wife when i get my new mac ;D
i dont mind portability if you ask me, but i love taking my 5 yrs old laptop everywhere or my iphone which is my new best friend.
i love screen size (currently have a 22") and i think the 13" MB is a bit small in the screen but i can still go to my old one in case that i need a bigger screen. Im also planning to use the mb (if i buy it) as desktop too.

now, i was thinking on buying the base model of imac or the base model of macbook. Is the base macbook more powerfull in the video card way than the imac?
I probably buy refurb to save some $$$ and use it to upgrade HD and ram.

ive seen some used ones on the net and if i buy a used one, is there anything that i should look for to make sure it is working 100%?
or should i skip used and get at least refurb?
any suggestion is welcome