@nathanu I have been considering a quilt for a while but parting with $400 has not been a priority.
The difference between the Enlighten quilts is essentially the foot box ...sewn vs short zip vs full zip. The Enigma has a sewn footbox, the Revelation has zipped foot box, the Conundrum has a sewn footbox and 3/4 length zip and the Convert has a full length zip. The Revelation and Convert can be opened flat where the Enigma and the Conundrum cannot but are lighter and less drafty around the feet.
UGO, Katabatic and Nunatuk are other good quilt brands. They all have long as an option although they deal with wide differently. There are a few others.
I have friends with an Enlightened Enigma Custom 20 and a Katabatic Flex 15 overstuffed and both are very pleased with theirs.
Katabatic use a bias cut to shape the quilt and are generous with their temperature ratings but they offer less custom options. A draft collar is standard. Enlightened tended to be less warm because they skimped on the fill (they may have addressed this).
UGO have lots of custom options and are generally well reviewed. They have an optional elastic tensioner option to help keep the back of the quilt tucked under. I think Katabatic do something similar as standard.
I haven't looked at Nunatuk that much but have seen them recommended and described as "the best"
There are variations in the pad attachment system which can be important for suppressing drafts...May not matter if you get a full zip.
If you are considering a full length zip then the Feathered Friends Flicker gets top marks and is generally available more or less off the shelf although not actually at the moment.
There are also some budget brands if you are less fussy and just want to give it a go. An issue with those is the whether the down is responsibly sourced. Also, I have not come across one that offers a full zip.