Help with a new grow.

Alright so i finally have the space available
I want to make a 5x5x6 grow box
I do not have sufficient funds for seperate grow rooms( veg & flowering )
so i will start with single and eventually move on.
I currently have none of the equipment needed, but i have saved a good ammount for a grow. so this is where i need your help.

What type of lighting should i use?
I want a 600 watt hps with a digital ballast, & reflector at the local Hydro shop, the guy offered me a 600 or 1000 electronic ballast,bulb, and reflector for around 300. Would this be a good deal?
Although if investing i would prefer a digital because i have heard better things. Any output on this? is it worth the money?
What bulb gives best result? should i veg with a MH and switch flowering over to the hps? or is the difference not very big?

What kind of ventilation will i need for this box? cfm?
I put in one fan blowing in and the other blowing out right?

and will a oscilating fan still be required? since the size is small

also i am assuming odor may or may not be an issue, in any case i want to de-odorize to reduce any risks.

I am only planning on growing 2 possibly 3 medium plants in soil.

Also I have been looking at attitude seeds, Can someone reccomend a potent strain? and company to pick seeds from? I prefer to get information from experience and not a sales pitch.

Sorry for all the questions, i am fairly new to indoor growing, i have done a few outdoor geurilla grows, nothing to crazy.
Thanks for all and any Help.

A fan is always best for optimal growth... while not a requirement it's a very good thing. 50-150 cfm would be good for ventilation.

Agro/horticulture bulbs work the best. Pretty much all manufacturers make them.

I suggest you start out with 2-3 times as many plants as you want to end up with. Males, disease, pests... Yea, make that 3x.

Depends on the high(s) you want. I don't buy seeds on-line.

When it comes to air circulation pushing is usually better than pulling(which is why homes/buildings work this way; however, the intake is usually pulled). Having two intake or two exhaust will be much better than one of each.