If you purchase two EFIS-D10A's, one can be used as an EFIS, and the other an HSI. You also benefit from having two fully redundant sets of flight instruments.
For the latter scenario, a FlightDEK-D180 + EFIS-D10A would work well (and give you redundant EFISes). An EMS-D120 + EFIS-D10A would work as well.