I've got the Terralux module except it's the one for the 2-3cell Maglite. So while it's not the same as what you are doing, they are certainly in the same family.
First to simply say what I've read, and that is that the 4-6cell Maglites with the Terralux aren't any brighter than the 2-3cell Maglites using the equivilant Terralux, but the extra cells in the 4-6cell lights give lot's longer run times. Both types are advertised as 140 lumens.
The thing is, simply changing to the Terralux is "supposed" to give you six times longer run times anyway (I haven't personally verified that) so I prefer the lesser length and weight of my 3cells since both modules put out 140 lumens, and the run times on 3-D cells is likely to be way more than I'll ever need.
Now to my actual experience; changing out to the Terralux is NOT going to turn it into some kind of barn burner. BUT, the Terralux is loads better than the original Krypton I replaced it with and it does turn a whimpy, lethargic flashlight into a lighting tool that actually has some use.
Another observation is that it's said in the advertising that a great benefit of the Terralux conversion is that you get to keep the Maglite focusing ability. Well.... yes and no.
I found that if you open up the focus, all you do is create a huge hole in the center of the beam, and it's very distracting to use it that way.
However, there is a little benefit in that what looks best to me is to open up the focus to the exact point where the center hotspot is even from edge to edge, and as large as it can get, just before it goes a little dark in the center.
At that point, you will have good looking spread with a decent hotspot that's best for most situations. I almost never move it from there.
Then the only other time I may play a little might be to tighten up the hotspot as small as it can be which is where you'll get the best distance throw. I do not, however, find that very useful very often.
In short, everyone who has an original Krypton bulbed Maglite truly needs to update it at least with the Terralux module. It's cheap, it's pretty good for what you have into it, and you won't be afraid to toss in the back of your truck where it'll get a little scarred up once in a while.
On the other hand, the Terralux, as decent and significant a conversion as it is for the Maglites, does NOT compare to other newer lights such as the MRV-SE, Tiablo A9s, the Deree DBS, or any of the other lights in that class that are much smaller, lighter, and can out throw and out spill the Terralux conversion (and probably most other conversions as well).
Having said all this, I have to confess that after using my Tiablo A9s and Fenix L2D/Q5 for a bit, I don't pick up the Terralux/Maglites much anymore.
I know you will be very impressed with your Terralux once you slip it into your Maglite, as I was comparing it to the original, but if you take the next step and get any of the other lights I mentioned above, you will be blown away by the difference.
