i have never heard anything good about mad dog psu's, i would be weary. be careful when selecting your psu, it is one of the most important things in your computer...it supplies all the power, hence if it is crapy your system will have probs. I KNOW THIS FROM EXPERIENCE! if you're looking for an ATX2.0, 500w, 24pin psu then i would go with the Fortron "Bluestorm" AX500.
http://www2.newegg.com/Product/Product.asp?Item=N82E16817104934
i have this psu and is very stable, looks great, has a reasonable price, and is highly rated and recommended. you can search for it and easily find some reviews. remember, parts are all about marketing, don't pick something just b/c it's highly advertised, investigate it first.
www.ocforums.com would be a good place to get some info on parts you are unsure about. just a quick example, i wanted to get a water cooling system and i asked people on there. in less than a week i had decided on all my parts and learn so much i felt like i'd been studying for a week. that's it.