Another iMac vs. mac Mini question

Everyone on these forums has been really helpful with things I have asked in the past, so here goes another question.

Should I buy an iMac or mac Mini? I will be using this computer for day to day stuff but mostly and mainly photography. No video editing needs for now, perhaps I will do that in a year or two when upgrading the DSLR. I am planning on purchasing LR4 as well. I'm trying to stay as close to $2,000 as possible. I have a Rebel XS, 10 mp raw files, currently have a library of over 10,000 photos. I'm looking for something much, much faster than my current, old Macbook.

Comparing the base 27"iMac, 1TB HDD, I will be upgrading the ram to 32GB vs. $799 mini, upgrading to 2.6ghz i7, will be upgrading to 16gb ram and upgrading to a Fusion drive, then buying a display separately.

Which is the best solution? First concern, I know the iMac has a dedicated graphics card, the mini does not. What affect will that have on performance, if any? Second concern, the monitor to pair with the mini? Is there a great monitor in the $300-$400 price range that would be comparable or better than the iMac?

I want performance, the ability to upgrade in the future is a little concern but I want the best bang for my buck.

Thank you!!!