Hey brother I got your PM and I'm going to post up some of your space requirements here in case anyone else wants to chime in:
I need 1000 watts, I started with an 8x8 w\ 8 ft ceilings but cut it down to 4x8 so I could get away with less lighting. I want to run an 8 site dwc\scrog. I also would like hps\mh combo in the same reflector. Could I run that with an ordinary ballast or do I need something special?
If you could help with any of these I'd really appreciate it.
Thanks.
A 4 foot by 8 foot area is 32 square feet.
A general rule of thumb (not set in stone, just something to shoot for) is around 50 watts per square foot with HPS/MH (some do less, some do more.)
1000 watts divided by 32 square feet = 31.25 watts per square foot.
1000 watts in a 4 x 4 area (16 square feet) is 62.5 watts per square foot.
As for whether it's cheaper to buy separate? In my opinion, I think that's better answered by your electrical skills, ability to get the parts for cheaper, not having customer service available and relying on individual part warranties. Plus, what's your time worth to you? A few minutes on Amazon or an online retailer can have a fully functioning quality assurance tested warrantied light that's been product tested shipped to your door. Boom. Done.
Most magnetic/electronic ballasts I've seen are switchable (my 1000W magnetic has a physical HPS/MH toggle switch on it.) I have two electronic 400W ballasts that do not need to be toggled (you can swap out MH and HPS freely.) Many of the electronic ballasts that you find on the market are also dimmable, give you 100%, 75%, and 50% power options. That can be huge depending on your environment/situation.
You can either buy MH and HPS separately, or you can buy dual spectrum bulbs that cover the wide spectrum from start to finish (more expensive.)
Hope that helps answer your question bro! Maybe someone that does DWC could better answer your requirements in that regard (I'm a soil guy myself.)