While looking for K1000 amps, I regularly checked audiogon listings for speaker amps. There are a lot of choices at around $400... Baby Sophia Dynaco ST35/70 Almarro A205A
There are some sparse impressions posted about K1000 + Sophia/Almarro amps. I eventually ended up getting an RKV to hear the famous RKV+AKG synergy
Also, I've been reasonably happy with DAC1's internal amp + K1000 (after getting a decent XLR->TRS converter). I expect that a well designed ss headphone amplifier with sufficient headroom would be quite satisfying. Maybe M3 or Gilmore Lite (both with upgraded power supply).
Go for the K1000s! And you won't even have to spend extra to recable them