While I can't comment on your rack questions, we had a window mount AC unit exhaling into a warehouse area mated with a small pump to move the waste water to a drain (VERY important this, unless you want mold on your walls). When we added our latest server (sixth one) we overran the capacity of the wall mount unit and had to go to what's called a 'split' unit. The heat exchanger and fans are in a panel in the server room wall, while the compressor and motor are remote mounted. This was about $3500 installed. It works very well for our six servers (three big Dell dual processor/RAID5 towers and three re-purposed workstation towers). The server room now stays at nice chilly 65 degrees.

We might have been able to use a larger window unit, but doing so would have required re-building the wall substantially. I'd consult with a local heating/cooling contractor.

-Zeke