Hi,
The well water option is the most econiomical but they are prone to the odd problem with blockages and other well problems. It becomes less economical if you drill a reinjection well as your costs for drilling will be high. Are you putting the water back in to the ground afterwards, using a reinjection well, if not where is the water going after it is used for heating.????( hopefully not the sewer ) If you have the $$$ i would ask how much more they would charge to do a Closed loop system and keep it simple. Your grant will cover you for 6300 on this system. Hope it helps.
Any questions PM me.
Cheers,