Light set up Single 400 W MH and a 600W HPS combo or 1000w hps

[Tricks]

I posted a reply with this post earlier, but started my own thread because I need an answer ASAP...my buddy's plants have been ready to flip for at least 2 weeks but we didn't have the money to buy the light and ballast until now, so this is what I'm wondering My friend has a 400 W MH and a old style ballast ( all brand new) he was going to go with a 600 HPS for flower, the light ballast combo I read about would have been perfect! a ballast that runs a 400W MH and a 600W HPS, all you do is switch out the bulb. We are using the old style ballast because there are only a couple bulbs made for digital ballast, and growers are reporting burnout rates of bulbs in as little as 6 months. So anyway, now he has to buy another ballast and bulb. 2 questions, how much does that combo cost and is it quality (I'm going to Google, just haven't yet), and even more important, what about using a single 600 HPS in a 5X5 area? we thought about switching to a 1000w hps, but I read somewhere that a 400 MH & 600 HPS are the perfect combo, especially on small grows, ...what do ya think? Peace