Might not be unless you use alot of 12V lines (as in extra HDs). So if the supply is equivalent to what a 500W one is for the motherboard, but provides more 5/12V for hard drives it might be worth getting anyway.

Mostly you have to get what is available for the price you want to spend and make sure it does what you need. Some people also like to match the case color to the power supply (black PS in a black case for example).

I never seen the need to use a $100+ supply in a simple home setup.