This code:
  SELECT_AMGP;
  nIgnore = m_cSPI.Transfer(5);
  nIgnore = m_cSPI.Transfer(10);
  DESELECT_AMGP;
Is producing this output:
  ...
  17631: 5
  17632: 5
  17633: 10
  17634: 10
  17635: 5
  17636: 10
  17637: 10
  17638: 10
  17639: 10
  ...

While this code:
  SELECT_AMGP;
  nIgnore = m_cSPI.Transfer(5);
  DESELECT_AMGP;
  SELECT_AMGP;
  nIgnore = m_cSPI.Transfer(10);
  DESELECT_AMGP;

Produces this output:
  ...
  758: 5
  759: 5
  760: 5
  761: 5
  762: 10
  763: 10
  ...

Finally, this code:
  uint8_t nDelay = 5;
  SELECT_AMGP;
  nIgnore = m_cSPI.Transfer(5);
  Delay_ms(nDelay);
  nIgnore = m_cSPI.Transfer(10);
  Delay_ms(nDelay);
  DESELECT_AMGP;

Produces this output:
...
1036: 5
1037: 5
1038: 5
1039: 10
1040: 10
1041: 10
...