Just got Audible Illusions L1, but it sound harsh

Now I set the left and right at about 6:00, and the main knob around 8:00. It seems it is better, I don't know why. It seems the harshness becomes more prominent when the main knob is set to very low (close to 6:00).
For another tube, it seems the 6h23neb is agreed as the best choice. So, I will just try another set of 6h23neb?
for the interconnect, any suggestion on the brand, or the material (like copper, silver, copper-silver alloy, cryogenic treated copper, special drawn copper .. etc)?
If I am still not satisfied, I guess I will sell it out and try a all tube, like a Cary SPL-9x

You have a truly great preamp there. It is essentially the line stage version of my Modulus 3A. Do your Energy speakers use metal dome tweeters? I ask because I had speakers with metal domes and the sound could be a little shrill. I now use speakers ( DeVore) with a silk dome and they are much better to my ears. It may be the Rotel amp is of much less quality than your preamp. The preamp can be very revealing. I use MIT cables, the long discontinued Terminator 2 cables.

I would try the preamp with a better power amp and or try different speakers. It definitely isn't the preamp unless there is something wrong with it. As far as the preamp not using all tube rectification, that is total BS, The solid state power supply does not make for grainy highs.

Yes, my B&W has a metal tweeters. It is a bit hard to upgrade or try out different speakers due to its size. The next speaker I want is B&W N802 .. but it is kind of expensive, and I want to pick up, so, I need to wait until it comes up.
As for the amp, I am tempted to get a McCormack DNA-1 or DNA-125. Again, waiting for a Rev A or deluxe version to come up. BTW, is it a good match with the L1? Other models I have been looking are Belles 150A, or Aragon 8008/4004. But from the reviews and comments, it seems the McCormack are better. And I just post another thread asking for the difference between the DNA-1 and DNA-125. But in the mean time, I will try another set of tube first, or some interconnect.

Gte357s, you are on the right track with the McCormacks. In fact I have used the AI L1 with an upgraded McCormack with great success. I have spoken very highly about the L1 in the forums. My reference to a mediocre preamp in comparison to a high quality amp has nothing to do with the L1 but was trying to point out that one quality component can improve the sound of the other. There is no perfect preamp but the L1 gets alot right. However the ultimate tube preamp would be one that has tube rectification (no solid state devices) and ultimately will dispense with even the slightest detectable grain, but may lack the dynamics of the L1. There are some sacrifices with any design.

I'm using the Audible Illusions L1 with a McCormack DNA-0.5 driving Vandersteen 2ce-sigs and am very happy with the combination.