Hey Locus,
I live in Vancouver and I have also been asking these same questions over at Ocean Quest. I am a coldwater recreational noob but I can share our thought process so far if that is of any help.
Backstory: My husband and I are fairly experienced tropical open water divers but we have now decided to venture into doing more local coldwater diving so we are converting to the longhose set-up. We have two sets of Scubapro MK25 and S550's but we need to upgrade our gear from the octopus/AIR2 recommended AAS we were advised to purchase when we bought our gear in the Caribbean.
First off, we considered buying another pair of Scubapro S600 second stages. Scubapro is a very familiar brand worldwide if you travel to remote destinations - which was our original reason for buying Scubapro. Also, we could keep the current regs we own since we wanted redundancy in our gear rather than mixing and matching. However, because we got kicked off the parts for life program for not servicing our regs annually, and Scubapro parts is not cheap, we were told it would probably cost double to service the Scubapro regs compared with other brands.
So we were advised at Ocean Quest to buy a complete new Apeks package with the DST first stage and XTX50 second stages since they have a very good reputation for tech coldwater diving. We were told that the Apeks parts for life warranty program is much more liberal in their servicing requirements. And although they are also an expensive brand, we were given the impression that Apeks was definitely better quality.
When we asked about the HOG regs which seemed very popular among DIR divers, we were told that the second stage is much heavier and can lead to jaw fatigue when compared to the Apeks. We were also told that the parts inside were not as high quality. And although you can save money by servicing the HOG regs yourself, you are actually supposed to take a course and be certified before you order the service kits. In addition, we were told that you will need to buy special tools to service the regulators. All of this didn't seem worth it unless you owned quite a few sets of regs (which technical divers certainly seem to do).
Finally, just to be thorough, I also briefly looked at a couple of other reg packages being sold online that was less expensive than Apeks so you may want to check out the Hollis DC1-212 package at DRIS:
http://www.diverightinscuba.com/cat...ators-hollis-dc1212regulatorset-p-2656.htmlas
I get the impression that Hollis is also a very reputable brand with the coldwater tech community. It seems like really good value for $425.
FWIW, I have been very impressed with the knowledge and customer service at both Ocean Quest and DRIS.