I'm afraid so. Without sunlight or at least indirect sunlight, HID is the only way to go.
You are on the right track. I bought 3 - 400 Watt factory MH
lights at a flea market for 30 bucks apiece. I took them apart and added a long cord to make the
ballast remote. They were 220 volt but being an amateur electrician, no problem.
Just don't forget to buy new
bulbs. Just because they still burn don't mean they don't need replacing. Every year for MH and every two years for
hps.