hey all, i'm fortunate to have 2500 dollars to spend on a retina iMac from my employer. we get an education discount. i have the ability to upgrade one item... and i'm wondering what i should do. my main use will be running/compiling programs that deal with large text-based datasets (i'm learning/new at this...), as well as using this machine for novice photography needs (family photos) and general computing. i've been struggling over two things... 1) 256 ssd + external hdd (wd my book duo) or the fusion drive? i've never dealt with having an external hard drive -- is it inconvenient? slower than accessing internal hdd? 2) one upgrade -- i7, 512 SSD, mx295? any thoughts...? have a 256 SSD with the mx295 ordered... keep going back and forth.