consider underclocking
Part of your solution will depend on the performance you have to aim for. I would respectfully suggest avoiding AMD processors, known to run hotter. Also suggest considering UNDERclocking, which could mean you are able to build a system which can extract all the heat purely by heatsink and convection. This will make a near silent PC - but you do not state if your aim is silent or quiet. You can look at the commercial model pre-made by Hush technlogies, a German outfit. They look very sleek and have been well reviewed for what they are (they also cost about twice what an equivalent performance pre-built machine might!).
Now if none of that makes you happy there is another cooling option for those with very very deep pockets.... I have forgotten the name of the system, but it uses a physics phenomenon to exchange heat by electric current and with that you just have to consider things like extra PSU load (you'll have to start getting VERY clever and expensive for a silent PSU) plus extra case room ,,, ah yes just remembered the name "Peltier Thermoelectric cooling modules" Google on that and be prepared to get shocked by the prices.
Trust me though, for a quiet PC it is kinda like the ultimate solution!