30CFM air flow. Noise floor not higher than 29 dB. A tube of good thermo paste. The higher the value, the better. Special attention should be paid to safety of a CPU's crystal. Too tight installation of a cooler can lead to mechanical damage of a die, too soft one can result in fall of efficiency of cooling, and therefore can cause overheat.
Special stress is to be laid on a general ventilation inside the case.
It's desirable to have one-two additional fans beside the fan mounted in the power supply unit. In principle, without overclocking you can take any PC133 memory. The higher the memory quality, the higher frequencies and less latencies. This possibility depends on a certain lot. To my mind, the performance should be divided not by a CPU price but by a price for the whole system block.