1000w hps magnetic ballast vs 600w hps digital ballast

I currently have a 1000w hps with a magnetic ballast with a 4' light mover. The electric bill has been kind of high and I was considering switching to a 600w with a digital ballast on the same light mover. Do you think I will see a dramatic decrease in my harvest?

Dramatic? No. Your harvest will not suffer by swapping your thou for a 6. I'm interested in which digital ballast you may be considering, because they are NOT created equally. I've got my eye on this one...

http://www.growshop.com/product-news/reviews/quantum-digital-ballast-review.html

Well 600 is just over half of 1000w.. So really it is a big step back.. But i think 600's and more efficient for sure.. You can still get good results..

almost off topic but you know what you should do? USE CFLS!!!!.......for lighting your house. lol, Anyway though if you havent done so yet go get yourself a few packs of the 13w cfls and replace any halogen(incandesent) bulbs with em. I went from using like 800 watts to light my house to around 200 watts. so it offset my 400w hps light and my fans and how much they used. Or have you already done that?

It will take a fair while to pay for the cost of the 600W bulb and ballast.