Simplest setup for seed starting is fluorescent lights nearly touching the top of the seedlings. Use as many lights as you need to cover the seed trays you have. Use a fan also, the tubes will seem hardly warm to the touch but the heat can build up.

An even simpler solution to leggy seedlings is to keep them cooler, especially at night. Most seedlings aren't designed to start out life at 70F day and night. I start out my bedding plants each year without lights and I have a lot less natural light than you.

You may look at my lighting setup. Right now I'm running a bank of 10 shoplights covering a 4 x 6' area. I'm growing rose cuttings, bergamot and peppermint. The plants are all nice and squat and bushy. Use 5000K fluoros, you can order
T10's from businesslights.com or Ushio or High output TCP lamps from that outfit.
I ordered my shoplights from cheaperlights.com
Get the Lithonia 1241CW. They're good and solid and have nice functional reflectors on them. Paul Mozarowski.

Here is a link that might be useful: My T8 garden setup. You can also use high output T10's if you want to keep ur T12 ballast.