1U Rack Mount CPU for 6700

Take a look at the Hystou line of mincomputers that are fanless and operate on 12 VDC. I am  using one of my 6500 remotely and I never turn it off as it only uses 12 Watts of power.

Jim, K6QE

Oh, I see there is a video adapter option: HPE NVIDIA Quadro K2200 PCIe Graphics Card, 4GB GDDR5.  Comes with a display port connector but it bumps the price of the server up by a fair amount.  Put in 8gb or 16gb RAM, a couple of SSDs and one of these video cards and I would think you would have a pretty nice server for less than $2,500.

I'm doing something similar -- 6500 in the basement -- but haven't found the need to but a computer anywhere but at the operating position. The only only connection between the 6500 and the computer is by ethernet. A 3ft cable or a 300ft cable will work as well. I do need connections to other equipment in the rack though. For those I use a USB to Ethernet adapter. There are threads here discussing some options. But to get closer to answering your question, 1U servers tend to be loud and hot. You might not care about the sound but you will need to be careful about the heat. HP makes the Z200 line of office desktop machines that are quite nice. They are quite, come with great graphics options (up to 5 display port monitors) and the mini-tower versions are rack mountable... but are 2U.