Finally getting a Mac...just a few questions

Hi everyone! I’m going to be buying a iMac soon and I’m just tearing my hair out deciding between the 3.1 i5 w/ the 1GB video card vs. the 2.7 i5 w/the 512 video card. I plan on using it mostly for Logic 9 audio editing, maybe do some video editing in the future with Final Cut, and watch HD movies on it. I also plan on taking advantage of the 2 new thunderbolt ports to connect additional monitors. Will the 1GB card improve the performance of Logic 9 and the additional monitors? Or will the 512GB be sufficient enough to power additional monitors without it being laggy or taking a performance hit? Does the video card make that much of a difference if I'm not gaming. I also noticed that I can buy a refurbished iMac. Has anybody had any issues with a refurbished iMac? I’ve used PC’s pretty much all my life and this is going to be my first Mac! Any information is appreciated Thanks.