I agree with Glreno, that transformer-based passive attenuators are the way to go. I'm using a DIY Bent Audio TX102, which should be very similar to the Silver Rock (I'd like to know how they actually compare), except that it's a bit more versatile and not quite as expensive.
What I want to point out is, that transformer-based passives don't have any of the drawbacks (impedance matching, requirement for short interconnects) of the resitor-based units and as such they are IHMO the best thing since sliced bread.
What I want to point out is, that transformer-based passives don't have any of the drawbacks (impedance matching, requirement for short interconnects) of the resitor-based units and as such they are IHMO the best thing since sliced bread.