My experience:
For XMR cpu mining is far and away more profitable in large part due to stability. GPU mining had the benefit of flexibility in that you can switch coins; however, CPU mining has the stability rivaling an ASICS. My 32 cpu opteron c7000 blade chassis has been running 24/7 under max load since August 2016. Zero crashes. My GPU rigs I restart weekly.
Oh ok. Well, electricity is no problem for me now. Should I restart PC every week? I will use GPUs mostly. I still don't know what CPU is in that PC I hope for 45nm Core 2 DUO, HP says PC can run Core 2 Quad 2.66Ghz, but on mobo specs it says Q9xxx so it could be 3.16GHz. But I'm worry about heat so I think it would be more wise use 65W Core 2 DUO than 95W QUAD. I have i7-870 and that beast is powerful CPU but also good oven.
Chieftec is by and large poor quality and unlikely to provide it's rated watts (or die quickly if worked hard). I don't know about MS-Tech, but usually cheap price is a bad sign for a PSU. Zalman makes some decent products and I think that model would be a safe buy. For a rig that is going to be mining 24/7 you will save money in the long run by buying a Gold or Platinum rated PSU. The efficiency isn't as big of a deal for general use with a few hours gaming, but for 24/7 mining under heavy loads the extra efficiency does make a difference.
Today I've bought R9 380 Nitro 4GB for 120 USD.
What PSU I need to run 2 of these and 1 less powerful GPU? And what PSU for 3 of these? What do you think?
Thank you guys for advices, very helpful for me.