Seriously!,
Items like computers, regulators, anything that your LIFE actually depends on... Get it from your LDS... You might think that it is cheaper on Ebay, etc. but I see horror story after horror story about unwarranted gear when purchased this way. What initialy seems like a deal, can turn into a nightmare very quickly... I'll give you a for instance. I like Suunto computers and started out with a cobra. After about four years, my cobra started to fail. It was reporting a depth of about 10 feet lower than actual. That is a big deal. I dive deep, so ten feet means alot. I purchased my cobra through my LDS. It was now out of warranty, so I'm screwed, right? Not so fast, my LDS dealt with the manufacturer and was able to get me a substantial deal on a prorated replacement or half price on a newer different model. I ended up with a Helo2 (awesome!!! computer) for $600. These things were listed at $1200 at the time. They offered to replace my cobra with a cobra3 for $300.00. That too would have been awesome considering the warranty had long since expired. I have no regrets about going for the Helo2....
Now, to put this in perspective. An acqauntance of mine, (I call him nosebleed) got a cobra computer on the internet. It failed in a similar manner as mine after a few years use. The local LDS was unwilling to help him and he wasn't offered any sort of support for the problem. TOTALLY SCREWED!!!
My opinion is this... The money you might save by getting these items on e-bay, etc. is not worth the support of your LDS. Believe me, you'd rather have your LDS having your back when something like this occurs than to be stuck on your own with no warranty and no support. Your LDS needs you... They Know it... And they will have your back if you'll have thiers. Your LDS knows who is a customer and who is a good customer... It pays to be a good customer. These guys always have my back.