Starting with a 250 hps airn cooled or built in ballast what? The 250 can work well. Maybe at first keep em 2 feet away but try to dial it in as much as possible. How long you plannin on veggin for, and 18/6 don't hurt at all. Just less time to have the lights blarrin. Are you plaannin on usin the 250 the whole way through or what? Good Soil? Good ventilation? If you only got a few seeds take care of them and take a few clones asap just a couple weeks after the older ones that way if you only got a few femi's you'll have more to flower with and find a good mother. Wouldn't take much longer to do at all, as under a 250 I think you'll be happy especially if your environs right temps, room exchanging air, smell.