Also installing i7s and the like will just up the wattage (even if it's just 10-15 Watts).
Unless you plan using the hardware for other things, just get the cheapest Celerons, they'll work just fine for mining. Also, new coins usually drop CPU mining rather quickly anyway so I don't get the point of purchasing CPUs that cost as much as a good PSU, which is far more important.
Just my 2cts, I guess everybody's got their preference
wrong but only some of the time. one or 2 setups go with the ones below
a big farm with 100 setups go cheaper pentium or celerons
the best choice is an intel 6400t or a 6500t
used for about 140 to 160
older boards an intel 4670t or 4460t
ebay has plenty used pulls good sellers
4460t
http://www.ebay.com/itm/Intel-Core-i5-4460T-Quad-Core-1-90GHz-Haswell-CPU-5-00-GT-s-6MB-SR1S7-FCLGA1150-/391630333189?
4670t
http://www.ebay.com/itm/INTEL-CORE-I5-4670T-SR14P-2-3GHz-6Mb-5GTs-QUAD-CORE-45W-LGA1150-CLEAN-TESTED-/322338168386?
6400t
http://www.ebay.com/itm/Intel-Core-i5-6400T-Quad-Core-2-20GHz-Skylake-CPU-8-00-GT-s-6MB-SR2L1-FCLGA1151-/361835402191?
http://www.ebay.com/itm/Intel-Core-i5-6500T-2-50-GHz-Processor-6M-Cache-2-50-GHz-SR2L8-REFURBISHED-/112212307073?
These CPU have low power consumption. but they are quite expensive, at least more expensive than the Celeron ones.