Yes, Seagate are one of the better brands.
No matter which HDD you choose, try and keep it COOL. Hard drives don't like heat. I use an Antec case, which allows the hard drives to have their own 80mm fan, and would recommend Antec cases to anyone based on this alone. They also have great build quality.
I'm an Intel freak, so I wouldn't recommend AMD (burned me too many times, no pun intended).
The Power Supply is one of the most important things inside any computer, and for this you can't go past the Antec True Power PSU's. Get as much wattage as you can afford. With power, the more the better, and the more regulated the better.
A UPS is a great idea, for a similair reason. APC UPS's are great.
tomshardwareguide.com is a great resource, which I'm sure you've already found.
That's my two cents worth...