DAC placement

I have found that isolating them from vibration etc is helpful, a seperate shelf would be good but not essential. I have my transport and DAC sitting on top of a roller bearing platform which is itself sitting on my Star Sound rack. They are seperated by a set of Ceraball isolation devices with a VPI Magic Brick sitting on top of them. Probably overkill but sounds good. I have found that most componets sound better with a weight on them, does not have to be exotic or expensive.

Make sure it is below the digital source so that the electrons can flow easily to the DAC. ;-)

Seriously, it does not matter. Make sure it has a clean power supply, it is well ventilated, and cabling is no longer than necessary. Vibration is unlikely to cause problems with the sound of modern equipment but may affect tubes. Excessive vibration may shorten life span. Keep high voltage cabling away from signal wires and keep the unit away from high RF/EMI sources like transformers.

I think that any sound isolation or coupling is going to be more important on the DAC than the transport because any effects will be stronger in the analog signal. I know that at my local Hi Fi store they had Nordost Sort Kones under the PS Audio DAC but not the matching transport. I'm convinced of the difference that Sort Kones made for my SACD player, but I would attribute it to the D/A portion of the player.

Since your Dac is not tubey, you dont have to worry. I usually place mine besides the cd player. It is recommended to Leave a gap between your DAC and pre. (if you have one)

Don't be fooled. It can be just just as important to isolate solid state as tubes. In the case of the PWT and PWD both benefit from isolation treatment. I use Herbie's Tenderfeet with 2 Supersonic Stabilizers on top of each component. For proper results of any isolation system one needs to first locate the component where it sounds beat on the shelf if you are using one. Then experiment with footer placement, then component top weights. Besides the Herbie's products, I've used VPI Bricks, MpIngo Discs, Vibrapods and Vibracones, and cones of various makes and sizes. Some components, like my ARC Ref3 don't seem to need footers as the stock feet are good enough. Also if you can move your component racks so they are situated on the middle side walls, you'll hear a difference too. Vibrating components smear the sound and you can loose the subtle sonic details that can really make your system sound outstanding. Don't forget raising your cables offs the floor as well. I've found that each of these tweaks can improve the fidelity of a system and when they are all added up the difference can be profound.