Cold Water Reef Plan

[Dale]

If I could offer any insight at all it would be to determine what livestock you intend to keep and work backwards from that. If you are mixing species it gets very complicated very fast. A specific filtration system might service some species well while causing certain death for others. Dirty tank - clean tank??? Depends what you keep.
A related point to really consider as well is food sources. Unlike many tropical species that have commercial foods available to them, coldwater species are probably going to require live foods whether it be zoo plankton, phytoplankton or micro fauna. It may get pretty expensive to repetitively dose and skim your water column.
Also, where do you intend to keep the tank? If you set it up in an unfinished basement (or garage like I did) you could take advantage of the passive cooling offered by the cement slab floor. My sump sits directly on the slab and it pulls the temps down. If you go that route the insulated cooler/sump would be a detriment.
You can also reduce heat input by using a drilled sump and a larger inline return pump (not submersible). Tee lines off of the return to create more flow in the display thus eliminating intank powerheads that will add heat to the system. I eliminated about 5*F by doing this.

Just some thoughts to keep the ball rolling.