Difficult to compare the GK1 and the TLP; apples and oranges. The GK1 is a full featured preamp, with source switching, volume control, gain, full dual mono construction; the TLP has no source switching, no volume control, no gain, stereo design (both channels processed in the one tube), and a single power supply for both channels.
However, sonically, the GK1 offers much tighter bass, slightly clearer midrange and superior sound stage - I believe this is what you mean?
Tubes are under-run by design in both circuits; total plate dissipation in the tube is under 1.6W, so I would expect a life in excess of 15 years.
Cheers,
Hugh