I have both already. What is a good humidity range to strive for 40-60%?

I have never used HPS lamps. I tried reading through the information here, but it was confusing at best. I think I want to run a smaller setup than most on here. How many HPS would I need for my room to grow 3 plants? Where is the best place to buy those? Can I use both? Sorry about all the newbie questions...

Thanks for all the information so far...