Quick question - is this white noise a "hiss" or a "buzz" type of sound? If it’s a buzz type of sound, that means you have some sort of ground loop problem going on. If it’s a hiss type of sound, then it’s a problem with gain and receiver signal-to-noise / voltage output (see further below).
One thing to check is to make sure that both the receiver and the Jeff Rowland preamp are both on the same phase A/C circuit. Most houses today have two phases (since they support 240V circuits like oven, etc.). If both devices are plugged into different outlets, it can be difficult to determine if they are on the same phase. Having 2 devices on different A/C phases can cause noise (probably even the ground loop noise).
Otherwise, I agree with Eric in that the receiver could be producing a lot of gain noise. When your Jeff Rowland is in unity gain mode (home theater bypass), it is sending the signal through at full gain (i.e. there is no volume attenuation). This means it is amplifying the incoming signal greatly (which includes anything including background hiss that is in the source). This was actually a notorious problem in car stereo systems where most of the gain was at the amp side and the source/deck was only sending a very low voltage audio signal. This was addressed with decks that had a higher voltage output level.
A work around could be to take that input off "home theater bypass" and turn the Jeff Rowland volume all the way down. Then go into the Marantz speaker configuration menu and turn the front left/right speakers up all the way. Then do a test signal for center channel and left/right. Turn the Jeff Rowland up until the speakers are calibrated properly. You are essentially forcing the Marantz to output a higher voltage for the actual sound signal and reducing the effect of the background noise/hiss. The downside here is that you’ll have to set the Jeff Rowland to that exact volume whenever you want to watch a movie.
Check your interconnects to make sure they have good shielding and that the shield on each side of the interconnect are wired (you can use a continuity tester or multi-meter to test this). This can affect noise. I don’t know of a different receiver that would generate less noise than the Marantz. You’ll just have to test/experiment.
