Don't cheap out on the rings themselves. Most of the money spent is going to be on labor. So if you get cheap rings and save $50, it's going to cost you a couple of hundred if one breaks and you have to pay someone to open the lights up again.
If you can do it yourself, go right ahead and get cheap ones. They're still more likely to break, but at least you can do it yourself and the only thing you've cost yourself is time (and frustration). I'm not aware of any company that actually makes FX lights with the halo's installed, it's not like Honda's or 350Z's where you can buy cheap aftermarket Depo's w/ the rings installed. Every shop just takes factory headlights and modifies them with rings.
Either learn to do it yourself (it's not hard) or find the best shop you can. A lot of shops will cut corners and headlights are one area you don't want that. I've seen some really bad jobs where you can see the adhesive, or the rings fall off, or the headlight isn't sealed anymore, etc. If you learn to do it yourself, at least you'll know how it's done. If you hire a really good shop, at least it will be done well and they'll often have a warranty on the work. I'd avoid the whole "I've got a buddy who does it on the side".