System Upgrade

The Krell K300i is way more tube like then the Luxman if you like the Leben sound you would love the krell, many people who have heard the K300i can not believe just how good it is even compared to much more expensive gear.

The Gryphon is a bit dark sounding however their gear is fantastic.

If you like tubes the Synthesis A 100t is amazing and powerful and an outstanding buy for the price.

If you can bring over your speakers you can hear 6 integrated amplifiers in your price range.

Krell k300i
Norma Revo 140
Naim Uniti Nova
Micromega M100
T A Dac 8/Amp 8
Synthesis A100T

Dave and Troy
Audio Doctor

You have only 32 watts at 6 ohms? You are under powered.   I would also change your tubes. That system should not sound flat. Are you 100% sure all your connections are correct ? 

Thank you jepatey, but after considerable and very helpful insights i decided to sell the Leben because it just struggled (for my taste) with the likes of Classical, Opera and Choir music - these were the areas where it became too flat for my ears. I appreciate that many say that this is a wonderful match, but I became increasingly frustrated with the lack of presence when listening. 

To improve the sound to start with bicabling with good cables is not to expensive.I experienced a significant improvement with Van der Hul revelation bicabling.
Anothe but more expensive step is biamplification.This a secure and significant improvement.
Other not expensive investement is the sidecof power supply and goroundung correctly mainly in the preamp.
As well signal cables as MIT is a secure good investement.
About room sonic response is as well a not significant investment.Absortion of fist reflection, bass tramps in the corners and diffusion panels on the laterals and roof as well as on the back.
Assuming you have a correct location of speakers at least 1m fron back and lateral walls and correct location of listening posicion.
I went through all thise steps before passing to biamplification or changing the equipment.But believe me the sonic traitment of the room is key factor.
Hope this help.I do not know your equipment.
Regards
Javier

MIT and biamping Harbeths? Wonders never cease but I still appreciate Audiogon!