I use PS Audio Power Ports and are very happy with them and as Gs5556 mentions I believe they are isolated ground. I have used Pass & Seymore Hospital Grade in the past and feel they are adequate as well.
Since you have metal conduit which is bonded to the electrical system ground, and boxes that are also metal and bonded; you definitely need isolated ground receptacles. These are useless in plastic boxes. The only difference between a regular receptacle and iso. ground is that the device yoke in not continuous with the grounding terminal; meaning that your yoke and box cover are not bonded. I don't think much noise enters the system through device yokes, but a large metal outlet cover could possible transfer some noise. The NEC requires that all metal enclosures be grounded so this is unavoidable. Unfortunately grounding in itself is not a remedy for noise because the stray voltages see it as impedence causing current to flow.