I have been a faithful user of Samsung HDs for several years, and went with the 840 Pro SSD, paying a little more for what is generally considered one of the best SSDs. I installed it in the second optical drive and snaked a SATA cable to connect to one of the two extra ports on the motherboard of my 3,1, adding a connector to power it from the second optical bay. There are lots of sled adapters, I needed an adapter to fit the bay but had reducers for the drive sled lying around. The biggest problem was figuring out how to remove the fan asembly, but had a 90 screwdriver for that. Once installed, I transferred the O/S using Carbon Cloner, really simple and worked like a charm. Absolutely thrilled with how it works.
Having done that, I also added a second processor, I had a quad, because of how cheap the processors are. My only disappointment, ignoring that it was difficult to install because I didn't have the right tools and finding them was a pain, is that iTunes does not make use of multi-core processors. WTF.
In any event, this is why I hope Apple does not mess with the basic design of the Mac Pro. It is an elegant, upgradeable platform that is flexible and powerful. For what I paid, it blows out of the water any of the several crappy Wintel boxes I have had to buy over the years. Apple just works.