A couple of things from a technical side:
- Improve the usability.
I can barely see the news/feed/tags/contact links in the top right, because its black text on dark blue.
The links in the regular text don't have enough contrast with the surrounding text to make them stand out as links. Change the colour and/or make them bold or something.
If I can't easily use a site, I don't tend to return to it.
- Fix your code.
Invalid feeds can prevent aggregators from reading you properly (meaning people can't necessarily find out when you have new entries), and invalid HTML can reduce your search engine effectiveness (meaning you'll get less new people via Google/etc).
And a few other thoughts:
- Work out your current and potential audiences, and target them both.
You can target your current audience by not changing too much, and you can work out potential audiences with a bit of thinking and by looking at the fringes of your current audience.
Check your stats to find how people are finding you and what entries are most popular, and work with that information.
Headphones are for people that like sound, so consider also consider sound-related articles that perhaps are not necessarily headphone related but do involve sound/acoustics/etc, and/or that look at headphones from a different angle (eg: an article on how noise reduction works, some sort of competition involving photographing headphones in odd ways, or creating the best 3d model, or whatever)
- Get people to mention you. One way you might do this is to submit short articles to other websites, that will then link back to your own site. You could perhaps become the headphone columnist for a general audio site, and perhaps you provide one or two entries a month to the other site either instead or as well as having the article on your site. You give them content, they give you (as a writer/journalist) exposure, and visitors.
Hope that helps.