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Hello everybody! This is my custom Leben CS-300XS amplifier. Some parts were replaced: IEC socket (new is Furutech AC Inlet R with rhodium plated contacts), fuse 2A (Furutech rhodium plated), power cable (Furutech Absolute Power 18R with rhodium plated contacts too) and... wood side panels. Original panels seems too dark from my point of view.
Any improvement on the sound after changing th socket and fuse?
The WA5 (not LE) reportedly does a good job out of its K1000 port, perhaps the DNA Stratus would be worth looking into as well. These are exceptionally powerful headamps (WA5 has speaker taps as well), but with the HE Adapter you should be able to use the speaker taps of any tube amp safely, including your Leben.
The Cary SLI-80 is reported to be fabolous with the HE-6. I have the Cary, but not the HE-6.
Magick Man has both (and a lot of other stuff for comparison) and seems to be ecstatic about the SLI-80/HE-6 combo
I'll disclaim that I've not heard the HE 6, do not own one, and only have a vague idea of the power requirements.
The Audio Research VSi60 puts out 50wpc and can drive full size Magnepans (it's stable into difficult loads). The Manley Stingray might work, but it's not much more powerful than the CS-300xs. Primaluna and Mystere have a range of options that have between 35-50 wpc. VAC has the Sigma 160i at 85 watts a side. The Ayon Orion II puts out 80 in triode and 120 in pentode/ultralinear. There's the Raysonic SP-200 at 200wpc that retails for >$3000 but can be found for well under 2k. MastersounD also has a couple of models that might have enough juice (Due Trenta SE & Evolution 845). Rogers High Fidelity makes an EHF-100 and 200 (per channel the EHF100 is 100w peak and 65 rms and the EHF-200 is 200w peak and 112 rms).
It's by no means a comprehensive list, and I have no clue how they'd actually sound with the HE-6. I assume all would be used from the speaker taps since I doubt the headphone amps (on the few that actually include a headphone amp) are anywhere near as powerful. I just thought I'd throw out a sampling of the current market.