In article , David Megginson
wrote:

You decide that you can afford to install *one* new permanent system
costing from USD 4K to USD 10K this year, and possibly one in each
following year (but not for certain). Arrange the following list in
the order that *you* think would make your IFR flying safest, putting
the highest priority item at the top. If you want, you can assume
that you already have some kind of backup vacuum system. These are
currently in alphabetical order:

Electric AI (backup)
Engine monitor (i.e. EDM 700)
HSI (slaved)
IFR GPS (non-moving-map, at this price)
Stormscope (or Strikefinder)
TPAS
Wing leveller (or other general single-axis AP)

my order of preference:

Stormscope (or Strikefinder) - handflying or not, thunderstorms are bad
Single-axis autopilot - reduce workload
HSI - reduce workload
Electric AI - redundancy
Engine monitor - gotta keep an eye on the engine
IFR GPS - yeah, whatever
TPAS - is this a poor man's TCAS?

--
Bob Noel