It won't die since a phone or a tablet will never be as powerful as a pc can be and some people need powerful machines. I wouldn't even consider a normal sized desktop as my main pc since it would overheat with the use I have for it(and you can't watercool a phone and still be able to carry it...
It might be a bit on the low side, but it should be able to handle it. Hard drive don't take that much power and the rest(except for the CPU) don't take much power either.
I would have preferred something in the line of 500W but it's not easy to find a server grade PSU(which I would prefer to...
First, let's fill the question form:
1) What will you be doing with this PC? Gaming? Photoshop? Web browsing? etc
Massive storage, automated downloads, sftp server, web server, IRC bot, asterisk server and much more.
2) What's your budget? Are tax and shipping included?
Nothing very specific...