Separate dedicated A/C unit (Window) to PC directly (what I did previously) or box which PC sits in (may experiment here some).
Anyways you can control the A/C unit, bypass the current controls, basically power to the blower/fan motor and compressor and control the temperature how ever you like. Using a temperature controller to operate motor starters or solid state relays is not that hard, add in a few protective measures as in a power relay that opens if temperature gets too high that shuts off your computer automatically can be added while keeping it simple and relatively cheap. Previously I insulated a case to keep it from sweating and cold in, hooked up ducting to and from that case with snap on and off ducting to an A/C unit. Everything gets cooled, even stock HSF end up performing well when cooled to around 0 c. I ended up running around 5c-10c for the most part and test runs at about -10c (basically ICE would not melt inside the case). Case just got very obsolete and never redid that. Now I am more thinking any case will work if you just enclosed the case with a cool enclosure which will make everything much more simpler.
Window AC is noisy as hell. Also a Window AC will ice up long before it starts outputting -10C air. I have seen them ice up in open air trying to get down to 20C.