Bob,
I don't have the HK 990, was only referring to it as the only stereo component I know of that has room correction.
Room dimensions are 17'8" x 15'6" x 8'. Speakers are along the long wall - PBN Montana XP (not the XPS) L/R and PBN Montana SPC center. Speakers are about 16 inches from the front wall, twelve feet to the listening position. That is a bit of a problem since the back wall is about a foot away. Room is carpeted and there are metal window blinds but no curtains so that is another issue
Current source is the Oppo 83 > Lector Zoe pre-amp > Butler 5150, but only for L/R at this time.
I had a Raysonic CD-128 also in the system but pulled that out for the downstairs system. When the Raysonic was in the system, the sound was OK, not great, but I am pretty sure it could get better with some extra work in positioning, maybe trying different cables. I'd like to try a higher current solid state amp with the speakers
Listening to CDs via the Oppo is a little more fatiguing over the longer term. Sound is very forward, detailed but maybe a bit too etched so my thought was getting a better DAC via the 105 would be a start.
Again, I just don't want to go with a pre-pro until I decide to either keep the PBNs and buy a couple of their mini-monitors to complete a five-channel system or sell them and try something different. There are some things I can do (trying them along the short wall, getting some window treatments, even trying power conditioning that has been suggested.
Fixing the room should be my first priority. There is a local guy who offered awhile back to come over and take measurements for me so I will reach out to him and see if he is still available.
Bob, you also mentioned a sub. I don't have one but how would getting one help with the etched nature of the sound I am presently hearing?