Define "Cool it down"...
What everyone else has talked about so far provides no cooling at all--fans generate heat (marginally) and move air around and insulation simply resists change in temperature.
If you aren't married to the idea of the space being 68 degrees in the summer or whatever I'd think strongly about a Fujitsu 18RLQ/18CL. It's undersized for the space, I'm not gonna lie. But given the energy credit (which expires at the end of this year) you can get it practically for free and at 20 sEER you aren't going to actually cool a space that big cheaper (as far as I know anyways).
If you want year round "house comfort" you would step it up to a larger multizone (say a 36 condenser) and drop a few ports (2 18s or even 3 12s) and be basically as efficient but it won't qualify for the energy credit due to a weird technical problem so the initial lay out is definitely going to increase a lot.
Here's the thing... if you're going to be cooling/heating that elephant on a daily basis you can almost forget initial cost discrepencies between your choices because the cost of equipment is going to be dwarfed by the cost of the actual heating/cooling. I'd be looking for any way I could to increase efficiency.
Just my $0.02,
Michael Lawrence