First cost and design cost has always been an issue with GSHP. If its cheap and easy to put pipe in the ground where you are, GSHP is great, but you need to make sure you have enough pipe in the ground. That's not easy. You need someone who understands local hydrogeology well.
ASHP performance on an annual basis is worse than GSHP but closer than you'd think. ASHP performance is also easier and cheaper to accurately predict. If you're looking to combine water heating I'd look at Daikin Altherma or the hydronic attachments to mitsubishi's city multi system. Both of those systems have good low ambient performance.
I think something like the Altherma would be a cheap and easy "bolt on" solution to your energy cost issue by adding a hydronic coil to the existing propane furnace system (probably in place of your existing DX cooling coil). On the DHW side you could put the Altherma DHW tank in a preheat position in series with your existing and run your recirc to the Altherma tank if youre not comfortable with peak day performance and want to minimize your capital costs now.