I am very happy with the Audio Research tubed preamps that have the InfiniCaps, whether stock or as an upgrade. For me, they made listening to CDs so much better that I laughed out loud with delight at the difference they made! I started out with a modded LS-7 and soon after sold it and bought the LS-15 and the LS-16 for our two main systems. (The LS-15 and LS-16 come stock with the InifiniCaps, and have the added advantage of remote volume control.)
Direct-in CD players and even the finest passive attenuators can't overcome the inherent harshness of the majority of original digital recordings. Only a tubed preamp will help with that. Is that added warmth and smoothness artificial? Who cares!?! The alternative is either to throw away half my collection of CDs or run screaming from the room. :-)
Best wishes,
Mark H>