question re: poor bass response

Newbee, the room is probably an audiophile's nightmare. Overall dimensions are ~40x18x9 but a partial wall separates the listening area (24x18x9) from the adjacent "room". The speakers face the length of the room, sit about 10' apart and 3' in front of a set of built in shelves/bookcases.

Hammergjh, speakers are on Sonus stands with spikes, so isolation shouldn't be an issue. I'm curious, what amp did your Krell replace and why do you think the Krell gives you better bass levels?

The Krell replaced an Odyssey Stratos. Krell amps are known for their prodigious base response, and now I know why. The bass became palpable at all listening levels but very balanced, not overly pronounced. The difference between the amps was striking. I'm not knocking the Odyssey, but I never felt the Odyssey handled the woofers that well and the Krell handles them like a champ.

I suspect that your speakers are too small to properly provide low bass in a room as large as yours, let alone full sounding bass at low volume. Even with full range floor standers you would need some means of elevating the bass level due to the F-M curve discussed above to get good bass at low levels. Despite comments to the contrary, it is possible to utilize a sub woofer - it all depends on the crossover and amp which you use on the sub woofer. My objective would be to have a sub which operated independly of the main speakers and didn't start to roll off the high frequencies until 100 hz - that way you could turn it off for high levels of playback. If you don't want to invest in a sub woofer, equalizers or tone controls are your only answer, short of buy new speakers and amp/preamp.

Yes you may be underamping. But your main problem is likely speaker and seating placement/positioning, and their relation! If your speakers or seats are not coupling well in parts of frequency spectrum, you WILL get a weak bass response! Also, from a "height perspective", if your ceiling is 8', the standard Sonus stands at 30+ inches are too high in my experience! The speakers do better aimed up slightly on 24-26" stands at best!
Still, you need to put the speakers where you sit,play music, and move around near the room, with your head down where the speakers go!. Then you move around till the bass sounds right!...repeat for each speaker.This is the easy quick way to "earball" the response for each speaker. If you don't get your seats and speakers set up where they couple best for "flat frequencey response", you'll get poor overall response in the bass. You can also measure when you're done with test tones and a sound level meter to make sure. IF it measures reasonably flat from the bottom of the bass to the upper bass, you'll have dynamic, full, fast, accurate sounding bass!
Learn to set up speakers in a room, and you'll be rewarded. Also, if a large large room, don't expect deep room filling bass, as the woofers can't fill the room. Good luck

i would get a different amp and go from there.