I'm close to ordering liner, too. I'm looking at Simpson Dura-Vent Duraliner or Simpson Dura-Vent Duratech. They are both rigid liners, but I'm having a bit of trouble figuring out the differences between them (as if the names weren't confusing enough). Simpson's website sucks.
I found that Duratech is HT . It has an inner wall of .020" 430 stainless steel, and a choice of either a 0.016" 430 SS outer shell or a 0.021" galvalume outer shell (galvalume? Really? What is this, Dr. Seuss?).
I found Duraliner (under the "relining" link on the Dura-Vent homepage:
http://www.duravent.com/?page=4.php#), but it has no link for features, no explanation of what materials it is made of. It does say that Duraliner meets UL 1777 standards, as well as ULC S635 and S640 (Canadian standards), and it says it is the premium high-temperature relining system.
Duraliner is cheaper than Duratech, but I'm not sure why. I searched this forum, and I found some posts saying Duraliner has an aluminum outer shell.
As for Simpson, there were mixed reviews on their customer service, but all threads I read spoke to the quality of their product (excepting some ceiling connector thing--but I'm buying for an insert, so I didn't look closely at it).
I found the best prices at
Dynamitebuys.com, although they note that delivery might be delayed in this busy season.