Both Zapco amps are still available.
Pricing is now:
Zapco DC360.4 was $475, now $450 shipped
Zapco DC500.1 was $375, now $350 shipped
Buy both for $775 shipped.
The above pricing includes the SLDIN.T Balanced line adapters and SLDIN.06 cables.
My responses may be delayed as I'll have intermittent mobile reception while travelling.