The way this site has it is good. I personally do not like the darker styles. But if you are an expeirienced designer you can figure out a way to make it look good in dark, which is really hard I think. I would say lighter.
I do agree with Fry, as theme is the heart of the website. For example if you take a site of Chocolate, what comes in front of you? Exactly the colours/shades of chocolate.
Only the thing you need to take care of is the visitor shouldn't find it stressful to read the content on the site. And the colours of the site should be captivative enough to grab his attention, and for this you must consider, what he is searching for, what thougths he is carrying in his mind along with the search topic. I Think that's it.
My oppinion is that the layout is mostly defined by the domain in which the designer is creating the website. If it's a gaming site , the layout could be darker. If it's a business site it can be both ( but with large use of images ) , if it's a shopping cart , I think that a ligher layout is nicer.