So it's interesting. The DGX600 and it's siblings are putting out similar light to a 10W HID. These were considered primary lights a decade ago in cave diving and now are our cheap backup lights. It's amazing.
The reason these may be an issue when doing night reef dives is because of how tight the beam angles are and those are rather blinding. The downfall of going with wider beam angles, especially in OW is you can't signal anything. Not that you should ever be more than arms reach from your buddy, but most people have terrible buddy etiquette *usually from poor instruction*.
anyway, here's what I would do if the budget allows
Hog Morph 1000 Handheld Back Up Led Light ***Video Wide Angle Light***
Hog Morph 1000 Handheld Back Up Led Light ***Spot Light***
Get a pair of each of those, with one glove for each of you. The glove is 100% worth it.
Total is $350 with Piranha. Gives you each a video light and spot light. Video you'll want for night diving, spot will give you something to look into nooks and crannies while you're diving during the day, or signal at night.
https://www.amazon.com/dp/B00WDQTIN...TF8&colid=20R1B8EYPPCRL&coliid=I1C7VYKO0ONXEN
These are about the same price as buying from Piranha, but are much better batteries. $40 for those
https://www.amazon.com/NiteCore-D4-...F8&qid=1486401308&sr=8-3&keywords=nitecore+d4
One of these guys to charge everything properly at $32.
3/8
You'll want a small SS bolt snap for each of them so you can clip them off to stuff, so $20 for those.
Tie like this. Ask Piranha to send you like 10' of cave line with your order, they should be willing to send it to you for free
How to Attach a Snap | Dive Gear Express®
Total cost is going to be around $450 which is a lot of money for flashlights and I know that, but you get what you pay for. You'll get 2 lights each, with top quality batteries and charger, and a goodman glove. The glove is great because you don't need to hold onto it so minimize risk of dropping them and what not. The lights aren't cheap, but you get high quality LED's with multiple output settings *crucial for night diving imho and don't get that with the lights that you mentioned*, a push button instead of twist on and the LED ring around it to give you approximate battery status. The batteries are going to be a lot better than the cheap ones that come with the lights that you mentioned and will have shorter burn times and shorter lifespans. The charger will also give you a bunch of information about the batteries other than the "red charge", "green done" light that the others do.
You get the diversity of a video light which is huge if you take a gopro, even during the day, but you also get the spot light to highlight or to really poke through shadows or into dark holes, and you each get one of each which is nice.
Also remember that these lights aren't just "scuba" lights. My wife and I use my backup lights for everything so they don't just live in my dive bin. I keep one in each of our vehicles when I'm not diving, one lives in the junk drawer, my nightstand, I have backup lights everywhere. Since they're waterproof and use rechargeable batteries with an idiotic burn time if not on high *which you don't want to/really shouldn't do when on land, low is more than enough light and they get really hot*, you just don't have to worry about them like you do with a mag light. They're small enough to hold in your mouth if you're working on something and need two hands, fully waterproof for camping or being out in the rain, and that also means washable, etc.
These are also high enough quality lights that you will never out grow them regardless of what you do.