I ditched my rack mount servers when I came home one February when it was 20F outside and my AC was running. Just not worth the cost of operating them! I culled my equipment down to a pair of T110 quad core Xeon (with HT) Dell pedestal servers, and a build-from-scratch file server with eight 3TB drives, cheap AMD proc, mobo, and all with 16GB RAM. Drastically lower power consumption than my old setup (4 HP DL585 G1's) and more powerful as well. The T110's are setup to allow me to swap out the boot drives to change hypervisors in and out. They have dedicated 1 gig storage networks back to the file server where the vdisks for the VMs all live. Between the two I can run Xen, VMWare, or Hyper-V (my work requires me to work with all three) and on those I can run pretty much anything I need. I have some Cisco gear for when I need to play with it but for the most part those stay unpowered. I can simulate most of the networking for testing.
Other than that there is a pair of 8 port gigabit switches, router running Tomato Shibby, cable modem, Silicon Dust OTA networked TV tuner, and a wireless access point in the center of the house for phones/tablets. All living on a 4 shelf bread rack in my office.