You keep on saying he should get a more powerful PSU, but you seem to be missing the point that the 450w Silverstone unit is the most powerful that will fit; the SG05 only supports SFX power supplies.
Also, your power draw estimates are... off base, to say the least. 50 watts for fans? Really? Maybe if you've got a dozen or more or they're 150cfm screamers. Yeah, you can find 120x38mm fans that do 200cfm at 4500rpm and pull 20w, but if you value your hearing at all (like most people) you'll stick to <2000rpm fans, and those only pull 2-4w each. You'll be hard pressed to fit more than a couple in such a small case anyway.
Keep in mind power draw of a component is usually the maximum it can
draw, not what it actually will draw 99% of the time. It's also very hard to make all the components draw their maximum power at the same time. Take a look at these charts
which show the difference between idle, typical 3D (e.g., gaming) and max 3D (e.g., furmark) power draw for video cards. Idle is maybe 10-15% of max for current gen cards, while gaming is 60-70%. Unless you enjoying benching, you're not going to see 100% power draw on a video card.
Another thing you should be aware of is that most reviews measure the wattage at the wall
, which means it's the total power draw including the power lost to the PSU's inefficiency. Most PSUs are 80-87% efficient, so the measured power draw is going to be ~15% more than the components are actually drawing.
is one site that measures actual power consumption of the components directly, including the individual rail loads. Read this article
for a good overview of what a system actually needs. Even their highest end gaming system (though somewhat outdated) barely uses 500w under maximum benchmarking conditions
Also - re: "good quality" vs. "bad quality" PSUs: some cheap and/or older PSUs are rated at XXX watts but if you look at the individual rails most of the current is available on the 3.3v and 5v rails. Modern computers draw most of their current from the 12v rail, so that's what you need to look at when selecting a PSU. It's quite possible for a PSU rated at 300w to have more current available on the 12v rail than one rated at 400w, which would probably make the former a better choice.