SPCR

I want to build a VMware free edition EXSi host for home use. It would be primarily for testing, dev and other misc VM’s, nothing production. Most of the time I would use it with Linux servers but I'm sure I would have a Windows 7 desktop guest to mess around with too. I might setup one of the VM's to be a media server using Subsonic (http://www.subsonic.org/pages/index.jsp) and an external hard drive. Anyway I have a wall mount rack that would allow me to have a 16” deep server so it can’t be a normal rack mount box. The rack is in the master bedroom closet with my home automation equipment so I need it to be very quiet, preferably silent and low power. I was looking online at some of these fanless servers which I would buy except for the fact they are rather expensive and I can only find ones in the UK or Germany which would add cost due to shipping. I am not opposed to buying an assembled system just want to find the right machine. See links below.

https://www.deltatronic.de/en/19-rackmount-en
http://www.aleutia.com/products/m200-fanless-server
This is the rack I have, its the 19U
https://www.hammfg.com/dci/products/wall-mount/1459

Wish list:
Under $1000
Low power consumption
Silent operation, no moving parts, fanless
Quad core 64 bit (non server processor is fine)
8GB+ Ram 256-500GB SSD Rackmount case less than 16” deep
Multiple NIC’s
Rack mount anywhere between 1U to 4U, or a tower I can set on it's side inside the rack.
Front facing I/O ports (not important nice to have)
I would love builtin remote KVM (not important just nice to have)

How much CPU power you need? there are fanless Avoton 8 core and 4 core motherboards that have multiple nics, they are expensive though, but they are fanless.

8 Core
SUPERMICRO MBD-A1SAi-2750F-O Mini ITX Server Motherboard FCBGA1283 DDR3 1600/1333
ASRock C2750D4I Mini ITX Server Motherboard FCBGA1283 DDR3 1600/1333

4 Core
SUPERMICRO MBD-A1SAM-2550F-O uATX Server Motherboard FCBGA 1283 DDR3 1600/1333
ASRock C2550D4I Mini ITX Server Motherboard DDR3 1600/1333/1066
ASUS P9A-I/C2550/SAS/4L Mini ITX Green and Space-Saving Server Board DDR3 1333/1600 ECC/Non-ECC UDIMM

I did see those but I was hoping to stay away from Intel Atom processors. Maybe those would be fine I don't know. My experience with Atom's has not been good but that was years ago.

Do you know how an Atom would do with ESXi?

Why 4+ cores and why 2+ network cards?

The newer Atom processors based on the Silvermont architecture are much faster than the old Bonnell based Atoms. The easiest way to think about them is comparable to core 2 CPUs in speed. The current Atom CPUs will do fine with ESXi.

That being said, once you are past a couple of VMs you are more likely to be I/O then RAM limited than CPU.