It depends on two factors:
1 - how covert your lighting needs to be
and
2 - how sensitive your imager is.
You shouldn't have to spend a great deal, but understand these things put off a lot of heat. Heat kills componentry. Illuminators that don't address heat issues won't last as long. Also, buying no-name stuff isn't much less safer than buying the same crap from burle, pelco or diebold.
It really comes down to maintenance hassles. How many times you want to climb a ladder to replace a failing unit? I'd personally buy cheap, and take care to position them less like a searchlight, and more for a shadow eraser.
In other words, instead of one monster spot illuminator, I'd look at the surveilled area, and see if there's a couple of places some smaller floods could be positioned to give a better effect. If it is your goal, have someone walk the area before you commit, too. You may wash out details with too much IR, especially in the dusk and dawn hours.