There's a new system out there manufactured by Multi Aqua, http://www.multiaqua.com/ It's like a commercial cooling system that's been scaled down to residential size. Essentially, it's an outdoor chiller that chills a glycol, instead of air, the glycol is piped though the house in a big loop, usually 1" pipe, Individual air handlers are place in each room that requires cooling. When a room calls for cooling the zone valve opens in the air handler and allow chilled glycol to run though the coil, then the fan on the coil kicks on and blows cold air. It's a nice system, but can be rather expensive, and it's hard to find a tech that's familiar with it.
The Multi Aqua air handlers have drain pans that require plumbing, so they will dehumidify, but your right, chilled water isn't going to get as cold as a refrigerant system.
I have a quad zone Mitsubishi system. So far I really like it. It's nice to be able to control each bedroom independently and it's very quiet. It seems to dehumidify very well and keeps the rooms at a constant temperature with the variable speed fans.
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