Personally for me, I will use whatever the case came with and adjust AS NECESSARY.
At present, my box at home runs in an Antec P182 case. This has 3 x 120mm Antec Tri-Cool fans. 1 at the top, 1 at the upper rear, and 1 at the bottom between my hard drive bays and my power supply. On this box, I run an Intel Q9550 with a stock Intel cooler, which is overclocked slightly from 2.83Ghz to 3.40Ghz. My temps are low 30's at idle and around 58C at full load. No need for any additional fans.
My work computer desktop runs in an Antec 300 case. It has 2 Antec Tri-Cool fans. 1 upper 140mm fan and 1 upper rear 120mm fan. This computer is running an Intel Core 2 Duo E8400 with a stock Intel cooler, and is overclocked slightly from 3.0Ghz to 3.6Ghz. My temps are mid to upper 30's and my max is around 55-60C. No need for additional fans.
So, I'm living proof that with decent wire management, stock coolers, minor overclocks and daily used machines...having tons of case fans is not always necessary.