First: If you need an amp and preamp for $600 then an integrated is best. Second: Your budget calls for mid-fi speakers, so separates are not going to make much of a difference, if any. So an integrated is the way to go. A preamp/amp would also require more $$ for cables.
Considering your $600 budget, apartment space, and listening taste, I would say the Audio Refinement Complete integrated amp is the way to go. The AR Complete also has the clarity and dynamics for better speakers, so it affords you the ability to upgrade speakers later down the road.