You should look at 2-socket mid-range models of any generation you'd like to use. Higher end models are generally specialized CPUs for certain domains (HPC, ban

You should look at 2-socket mid-range models of any generation you'd like to use. Higher end models are generally specialized CPUs for certain domains (HPC, banking, etc.), so they're generally hotter. If you're not going to go full-throttle all day, every day, having SMP is good. For an homelab environment, I think 65W-95W band is ideal if you want to keep noise and heat output manageable. While it brings some performance hit, enabling frequency-scaling (SpeedStep in older parlance) is beneficial. Using a 2U server will bring noise lower since you won't be using, counter propeller, 10KRPM 40-50mm fans. If you want especially quiet servers when they're not under load, look at Dell PowerEdge. They run like sleeping cats when idle / lightly loaded, but scream like an agitated parrot if you heat them up. Lastly, a good way to maximize performance without too much power consumption is using an "optimal" RAM configuration which utilizes all channels with homogeneous RAM modules.