15 mbp: retina or not, or keep unibody macbook aluminum'08

hi all,

just bought a canon 7d dslr camera and was wondering if anyone has experience working with large images on their macbooks/macbook pros. the requirements on the canon box suggested at least a core 2 duo 2.6ghz speed. my current laptop is an aluminum macbook i bought in late 2008 which is core 2 duo 2.0ghz speed. it works like a champ for the most part after all these years, i just recently replaced the hard drive. but it's video card is not up to snuff it seems...for example when watching bloomberg, it only works on the laptop but can't put out on my external 27 led apple display. sometimes too on photobooth, if there are too many people in picture, the picture gets, i don't know how to describe it, but "digitally" for a lack of a better word lol. most streaming news stations don't work on the external display but work just fine on the small 13' screen.

so i was curious if i should get a 15" macbook pro or the retina 15. this is my first dslr. i plan to use the camera mostly for taking pics of my family and landcapes.

i've pretty much ruled out the 13" b/c i already have one and another reason is it doesn't come w/ a dedicated video card. just don't know if it's worth the extra $400 for the retina when i already have a 27 led display. the appeal of the retina is the display and faster hard drive. if i add that hard drive to the non-retina it's already more expensive than the retina! the discouraging part of the retina is the ram upgradeability.

any thoughts would be greatly appreciated!