the mother board will always be hot, the water cooling removes the heat more efficiantly.
just dont do stupid thing like hang your radiatior out the window becasue there is a chance that it might be below ambiant temprature thus creating moister which is bad. Along with water cooling get some...
You can use a foam but that would require good air flow.
in stead of getting a new case which you dont need to from what i see seems to be a good case. anyways. you and get a good heat sink with heat pipes i would recommed that xp-120 with a slow spinning fan, Antec has a good one. you can...
i woulod have to agree with rysher on this one. take the block off and see if you put to much paste on or to little. this is vary odd because it sounds pretty good.