Ralph at Atma-Sphere personally recommends the Mogami Gold balanced cables for his amplifiers which will cost you very little. I got mine from Guitar Center. There is no reason to spend more.
I also own an S-30 and listen to the advice above about tubes. Buy the right NOS tubes for the 6SN7's, and the amplifier becomes an entirely different beast. You will not experience the fatigue you mention, and everything will be enhanced.
I also own an S-30 and listen to the advice above about tubes. Buy the right NOS tubes for the 6SN7's, and the amplifier becomes an entirely different beast. You will not experience the fatigue you mention, and everything will be enhanced.