Krell amp with Zu Essence speaker

No,unless you get crazy with the volume knob.

Kinda overkill, isn't it? Zu specs state

Average Room / Moderate Volume 2 - 8 Watt
Large Room / Loud 8 - 30 Watt
Large Room / Concert Level 30 - 80 Watt

At least you won't have to worry about clipping and distortion!

With reference to Tpreaves's post, a problem you could have is that you won't be able to move your preamp's volume knob very far before you have earth-shaking volumes. I don't know what preamp you use, but many that use standard attentuators sound their best as you get about half-way (12 o'clock) on the volume knob, and some that use resistors (like my Jadis) may have much larger increases in volume for the first portion of the volume knob, with the finer gradations in attenuation/volume control as you get closer to and beyond the 12 o'clock position. In the latter case, it would potentially be more difficult for you to have just the right volume for your listening if you are stuck between 6 and 9 on the volume control.

Yeah it depends on the pre.It might be overkill.Some might want to use those Krells (or another amp they like such as the Parasound JC1 also400 watts) and then use passive pre so as to be able to attenuate volume not just a small amount and lose fine control.Passives which some like for neutrality but I have never do to lack of dynamics and bass.Zu has some wild spread on their speakers being able to run off SET 8 watts but rated to handle up to 300 or 200 continuous.So being careful you probably won't damage them but might have limited volume attenuation (like I have with a KRC2/KSA300 Krell but that because the pre output is to high a gain which is what RCprince was talking about but for mine it's over the full knob spectrum).Just my opinion but using those amp on a $3,500 speaker is kind of waste (but with Krell your going to get bass "grip" like no other and hear what those woofers can do).
If you have heard and like the Essence why not think about selling amps and match everything up best for Zu's?I always think speaker choice first amp and pre that match up to it's needs.It's a flexible speaker and you can choose a lot of gear to use with it but 400 watt amps I dunnuh know....
Cheers
Chazz