It's mini-itx but I was going with the E300 for the extra space for cabling and the ability to move to a FlexATX board in the future if need be. I have seen those fanless heatsink cases but how effective are they really? I imagine the case will get fairly warm with the CPU getting pushed hard to achieve as close to gigabit VPN as possible.Which C2758 board? Is it mITX or uATX? If its the mITX version have you thought about a fanless heatsink case instead?
I used these for a "customer" once - dead silent: Akasa Thermal Solution