Get celerons/semprons and A4 APUs, at least with the APU you have a gpu to mine on (only a few khash mind), Intel HD4000 graphics only get 13khash and an i7 cpu gets 50khash.
Then buy a M-ITX board and an i7 if you want to mine QRK/PTS or similar, may even fit in the same case.
Ok, thanks for your reply. I have some Semprons rigs, now I´m just analyzing the CPU coins mining possiblity.
Maybe the best will be to keep on cheap Semprons/Celerons and get some specialized not so expensive Xeons I have access to.