The reason why you need WC for TEC:
First, you need to understand how a TEC works. Basically, a TEC gets very cold on one side and very hot on the other side. After you hit 45-60W QMax or so on a TEC air cooling in not good enough, hence the need for cooling the hot side of a TEC with water cooling. Manufactures try to compensate for this by using heat pipes attached to the TEC then to fins (kind of liike a rad on a WC set up) to dissipate heat, but that's not very effective any ways.
I see no possible way of modding your ChillTEC. If you had asked before buying, we (probably Conumdrum,rubix,wuzy, or me) would have told you to get a water cooling system for about $50-100 more.
For more info on how a TEC works:
http://en.wikipedia.org/wiki/Thermoelectric_cooling