fengmian,
I think it mostly comes down to your source and whether or not you like the inherent sound of the K701.
The Lehmann seems to be generally considered a clean, transparent and neutral amp, which does not add much to the source it is fed.
My main setup is foobar -> USB -> Apogee Mini-DAC -> Lehmann BCL -> K701, and I find this a very pleasant and detailed combination,
where the Mini-DAC adds a bit of warmth, which seems to go very well with the BCL and the K701.
If your source is on the cold and neutral side, you might find the whole thing to be a bit too sterile.