Well, the product code is slightly different. For the Blue storms, its THN-R. The ones on that site are THN-P. I'm not sure what's the difference. Other than the color and mesh wrap on the wires on my Blue Storm, it looks very similar.
What other major PSU manufacturers are there at those stores? I haven't been able to find the link to get a list of the PSUs, I just did searches on quiet PSUs I knew of and didn't come up with any Seasonics, Enermaxes, or Antecs. The next best choice IMO is Fortron, which has fairly quiet, high quality PSUs.
The Zalman 7000AlCu used to be a SPCR reference heatsink because of its quietness, but since then some better heatsinks have come out. However, the 7000AlCu is still very good, especially since you won't be putting in a high-end processor. The Freezer 64 would be better in cooling, but it puts more strain on the motherboard because of its size and weight. I wouldn't recommend it over the 7000AlCu unless you're using a 3800+ dual core Athlon64 or something like that.
I can't say if the Silentium will be quieter than a Centurion 5 with a Fortron, but it looks cheaper and is another option. The Silentium might have a noisy PSU and fans which you'll have to replace anyways. You might as well buy just the case and get fans and PSU that you know should be quiet. I would recommend the 3000B, but the Centurion is only ranked slightly lower than the 3000. Read the SPCR reviews on both if you want more information: http://www.silentpcreview.com/article75-page2.html
Don't put too much trust in manufacturer numbers for the sound level. They all measure at different distances and with different methods. The general consensus on this site is that Nexus fans are the quieter than any other fan at 12V, but they don't move much air. Papst, Panaflo, and Yate Loon move more air, but are somewhat noisy at 12V (still quieter than most other fans) and can be quiet when turned down to 5-7V. I like these because they give you the ability for more cooling if necessary.
For the motherboard -
It looks like they just took off the stock cooler. I expected a larger chip/more chip surface than that, but then again, I've never taken off the chipset cooler on an nVidia chipset.
300W should be enough but you'll be cutting it close. As long as you won't be adding 3 or more hard drives/optical drives or many PCI cards, I think you should be fine at 300W.