i think you would want a regulator for NiMH, as the voltage drops when it starts to lose its charge/get drained. whereas LiON maintains a more constant voltage as its drained. i think for anything but LiON you want the regulator.
if you can contact batteryspace or trailtech i'd hope they could help? it's been so long since i looked at this stuff i'm not much help really.
when i ordered my lights they all came with regulators, and the one you linked to appears to come with one:
other than having to wire the lights up yourself and sorting out the battery issues (which can be a big PITA), the TrailTechs are really easy to use and no complaints in 3 years of use …
If you are going with Li-Ion, make sure the battery pack has a chip built in. Li-Ions do have pretty sensitive chemistry if I recall correctly and you want to be careful no to discharge them too far and not to over charge them or you could potentially have issues. Most battery packs from places like Battery Space should have a chip to regulate that.
A thread about HIDs, Halogens, and NiMH batteries? I had to check twice to make sure this wasn't a 2002 thread revival. LED and Lithium Ion batteries are the way to go. The Niterider offerings are well-priced and make building your own set more of a separate hobby than a price-saving item…
The Niterider offerings are great because they make it so easy to get ahold of solid LED lights. That being said, if you want that extra bit of performance, or thos extra few options, you are looking at a different brand of LED lights (Dinotte, for example) or you are building yourself a light. Another option is to buy a set of Niterider lights or something and then upgrade the LEDs to the latest bin.
If you like tinkering and know what a drill is, what a hacksaw is, and what a file is… you would probably have a great time with a DIY light. You can definitely save a bunch of money going that route, but I'm guessing most people don't save much, you have to shop carefully for that as shipping costs and things sure add up. If anyone is interested, I can post some photos from the light that I am currently building. You might be surprised just how simple it is! You can also search on mtbr or probably on google too, for the "achesalot" LED light… the creator of that light actually has a webpage with fairly detailed info for making a light just like he did… that is what I am doing and I sure can't wait to finish the wiring and fire it up!
…gah, I get a bit too excited about these lights.