Domain Relevancy and SEO

Hello World! I've a question.. I have an Amazon Affiliate Site doing so well right now.. 3 month old and did +260$ last month.

My website in a certain niche in Electronics, let's say Speakers.
I found another really easy keywords in another electronics niche let's say Mice.

"The domain contain Speakers word"

I tried one keyword of these keywords and ranked #1 with no backlinks at all after 3 weeks from publishing the article and got quite good sales from it.

So now, Should I do another…

Domain Relevancy and SEO