Digital ballasts dont put out any more light than magnetic ballasts. PERIOD. They use less energy on startup, and dont buzz, but most cause distortion on all the surrounding phone lines, I dont think this problem is so bad with Lumatech digi ballasts though.
The thing that DOES matter is the type of Bulb you are using, even a high output 600w hps is still nowhere near the 140,000k lumens of a regular 1000w HPS bulb.
600w HPS average 90 000 lumens, 1000w 140 000.
That being said the lumen output really doesnt mean anything once you start trying to increase your grow area, especially with 1 light. To increase your grow area you raise the light, and this loses lumens big time, this is why I would go for 1000w any day if I was using less that 3 lights at 600w.
As the light moves it diminishes at 1/distance2. 1ft= 1000 FTC (foot to candle) 2ft=250FTC, 3ft=111 ftc...etc.
Now that thats out of the way, an ouce per plant is definitely achievable, but I really cant say if you will achieve that without some pics.
Ideal conditions, with c02, veg to 2ft and lollipopped I would expect at least 2 ounces per plant under a 600, up to a max area of 3.5x3.5 outside that you will notice lower yields.
Absolute IDEAL conditions with the right strain, c02, vegged to 2ft and lollipopped about a pound dry, maybe a bit over COULD be grown under 1 600w light, but I would Expect 8-10 ounces and probably end up with 12-14 plus all the popcorn buds and hash I would make after.
Anyways good luck with the grow, get some pics up if you can!