The only way you can get the CPU below room temperature is with water cooling being included at some point. You can get a peltier - which most mini-mini fridges use, but you will need one more powerful than that, as your CPU will put out more heat than it can cool. With this, you need to get a peltier, attatch it to the top of your CPU - cool side facing it- and then attatch watercooling to the peltier to cool that down. and I believe you need to surround it all in foam and silicon.
Or you could do the chilled watercooling way, where I assume they have a fridge motor somewhere in it. look at xtreme systems
Anyway, start off with the case mod.