I feel a lighter theme is more appropriate for a gadget forum but you could always go with a dark light theme... That may not make sense but there's ways of making a dark theme come across as light 😛
Overall though, a lighter theme would suit it better.
I would go with a light theme, but make sure its not one that has been used a 1000 times before. If you can't find a theme that isn't widely used then maybe you should try the darker theme. There is no harm in trying.