Graham Slee Solo+PSU1 Vs. Lehmann Linear

I am slowly putting together a 'better' headphone based system. At present, I'm using a Graham Slee Reflex phono stage with a Solo (both with the Slee PSU1 power supplies) with a pair of Sennheiser 650 cans. (an Technics SP10 TT is in the house, and soon, an SME 12" arm will be part of the set-up too)

Although I am currently using a Graham Slee Solo with the PSU1 power supply, I think there might be better headphone amps out there- especially as I have my eye on a set of Sennheiser 800 cans... I have noticed that the Solo does struggle occasionally when pressed with very busy passages or a bit of extra gain. (not that I'm listening at 747 sound-levels BTW)

In my $1,250ish price range, I have whittled it down to the Lehmann Black Cube Linear from Germany.

The reviews on the Linear are excellent. However, I'm wondering if the change-over would be a step-up or a step-across? Other options? (I don't really want a tube headphone amp) Any 'Goners had experience with both amps?

Music? 70s to now- rock, pop and dance. I have a large collection of records that includes many dynamic, loudly cut 12" singles... The winner must have a firm grip on the bass (not shy either!) and excellent PRT.

I am also looking at a phono stages, but that's another thread....
Hi Dsa, I'm not sure if you already assembled your headphone rig. I use a HD800 driven by the Solo and the PSU1.
The combination makes everything right. I have the feeling that soundwise everything is perfect. Point.
Powerwise I never feel any limitations, and the combination is excellent for longer listening sessions.

Before buying a headphone amp I auditioned the Solo and the Black Cube Linear using the top of the Grado line. The Linear is very clear and extremely detailed, the Solo has more warmth and "more rythm". As you can see, I decided for the Solo, it was a clear decision.
A friend of mine has a Grado (GS-1000 ?) and the Linear and we auditioned our two headphones.
The Grado sounds much warmer than the HD800, so there is more synergy with the Linear. The HD800 with the Linear sounds extremely detailed with less lower frequency weight, I wouldn't recommend this combination for longer listening sessions. Regards, Joachim