You own a store, you sell 2 brands, which?

Really tough question as there are many great electronics brands that I would choose but very few that also have a turntable line.

Would probably have to second a previous choice with Linn due to their product categories of electronics, turntables, speakers and price ranges.

Speaker manufacturer is an easy one. Vandersteen hands down.

The OP did not say the goal of the subject matter was to select the two products that would be the most profitable. Suppose you are independently wealthy and opened the store for personal enjoyment.
In that case I would select two products that I would enjoy selling and have confidence in their quality and musical enjoyment.