Mannai in Salwa Road (opposite Jarir bookshop) are the agents for Jamo & Onkyo. They have a very knowledgeable Lebanese salesman, I was very impressed with his service when I bought an Onkyo amp. recently.

The shop is on the right from the Hummer showroom.

There are some other (top end) home theatre shops down Salwa Road as well. I think one is called Barzan, the other QDigital, or something like that.

Good luck.