Dvdgreco, if you do choose to go with an active preamp, I would think twice before choosing some of the models that have been mentioned. The concern in some cases being that their gain may be so high that you would be forced to use the volume control undesirably close to the bottom of its range. As was mentioned, the AMR 77.1 apparently has a full scale output of at least 2 volts, as most digital sources do, and your amp (assuming its sensitivity didn't change as a result of the "silver upgrade") will put 370 watts into the 4 ohm impedance of your 87 db/1W/1m speakers in response to an input of only 1 volt.
I note that the older Herron model you mentioned has a specified gain of 14 db, and the VTL model that was suggested has a gain of 13.2 (single-ended out) or 19.2 db (balanced out). And as with many CJ preamps, the ACT2 Series 2 that was mentioned has a VERY high gain, in this case 21.2 db. Those numbers are all too high for comfort, IMO, in relation to the relevant parameters of the rest of your equipment, although in the case of the Herron the issue may be mitigated by the 166 steps its volume control provides. I haven't checked the gains of any of the other models that have been mentioned.
I note, btw, that the currently produced Herron VTSP-3a provides an 8 db gain mode, in addition to a 14 db mode, and I have no doubt that it is a wonderful product. And like many other Herron owners I can attest to Keith Herron being an exceptionally wonderful person to deal with. However the VTSP-3a costs $6550.
Good luck. Regards,
-- Al