Jake,
Only your ears can tell you whether it is better than more expensive pre-amps TO YOU.
It replaced my US$3500 BAT VK-30 (with NOS tubes) and was better by a very wide margin. The BAT sounded slow, dark, undynamic, undetailed and very veiled in comparison. Although relying on some memory here, it also clearly bested other pre-amps I've auditioned including, Audible Illusions M3A, Electrocompaniet, GTA SEP1, Acurus, Arcam, Musical Fidelity, Perreaux etc.... and that was with the stock tubes and stock cermet pot in the GK-1 (later replaced with TKD's best attenuator and Siemens gold pin 7308's) and without any BlackGates, Rikenohms etc etc (that I still haven't got around to doing).
Darl, who voiced the GK1 with Hugh, found it superior to a number of expensive pre-amps including ML's and others. In older threads, comments have been made by others who preferred the GK1 to Bottlehead Foreplays, Audio Research REF 1's etc. Not bad considering the Ref 1's were US$8k+.
I doubt you would find a better sounding pre-amp anywhere for the price, and even spending up to US$10k would not assure you of getting a better sounding pre-amp. You would need to audition them to be sure. Chances are you could save some big $$$ and improve other aspects of your system for greater overall improvement. Plus, for tiny $$$ you can tweak the GK1 further for even greater performance or to better suit your particular tastes.
I'd love to hear a nicely modified GK-1 up against a CTC BlowTorch or CJ Art to see how much difference there is, but I sure aint gonna spend US$15k to find out.
Even if you did major upgrades to each of your other components, I doubt you would need to upgrade from the GK1. In fact, you may find yourself desperately saving $$$ to upgrade your other components so you can hear everything that the GK1 is capable of. I know I would certainly upgrade my Plinius SA100/3 and Sony SCD-XA777ES before I'd even contemplate replacing my GK1.
The biggest hurdle is getting your head around the idea that the GK1 can sound so damned good for so little $$$. I'm sceptical by nature so, despite all the praise, I certainly wouldn't have done it had I not been able to audition it myself. The difference was immediately obvious, but still hard to believe.
Tubes usually settle down in a few hours, although a brand new pre-amp could take several weeks to fully reach its best.
Good luck with your journey.