I'm happy to comment!
First, on pricing -- we definitely don't compete with building it yourself, and we don't try to. If you have the knowledge to pick the right components, the ability to put it together, the tools to test for thermals, balance the fans, ensure you're running at safe temps, and the patience to deal with any issues that may come up (including RMA'ing parts), then you can certainly save some money by doing that. We're here for the niche audience that understands the importance of quality hardware and craftsmanship, but who do not have the time or ability to build a PC themselves. And I think that audience is growing when it comes to quiet PCs. I've seen far too many people try to build their own, who end up inadequately cooling their PC.
Regarding components, we don't offer this setup in an AMD version mainly due to low demand. Maybe it is something unique to our target audience, but we see somewhere around 95% demand for Intel. AMD made a small gain recently with their lower cost 6-core CPUs, but then it quickly fell off again. Part of the reason why WE don't push AMD for a system like this is the mounting system. Intel simply has a superior socket when it comes to large heatsinks and shipping damage. We have never, not once, had an Intel LGA CPU come out of socket in shipping. I can't say the same for AMD, and when we're dealing with a quiet system with large heatsinks, that's a big deal.
As for why we went with the Gelid Tranquillo CPU cooler -- we tested about a dozen HSF units here at our facility. The trick is, not only did they have to perform well, and be extremely quiet, but they also had to be able to survive the stresses of shipping. The P55 chipset also presented a unique challenge, in that many of the coolers we tested blocked the nearest RAM slot. The Prolimatech Megahalem was a close second, but ended up losing to the Gelid Tranquillo because it only performed slightly better, but blocked a memory slot. Once we had the Tranquillo as a finalist, we actually built up a Serenity, and dropped it from our roof (therapeutic!). The HSF survived intact and fully seated
We continue to look for new and improved products however, so I'll be checking out recommendations given here. I know we already have some leads on some other Prolimatech models to try.