To the OP, I had the exact same issue with the A5's, and so I upgraded them to the A5+. Let me just say that the A5+ is what the A5 should've been. It's pure perfection. The biggest gripe I had with the A5 was the automatic sleeping "feature," which automatically turned off the speaker's amplifier after about 15 minutes of non-use. The big problem with this "feature," however, was that every time it turned off, it would make a loud popping noise. But with the A5+, this "feature" no longer exists. In fact, it comes with an actual feature of being able to hibernate the speakers with a click of a button on a remote. It's really nice!
Moreover, another problem with the A5's were that at low volumes, the sound would become unbalanced. But with the A5+, this problem no longer exists. Even at low volumes, the sound is balanced correctly. Furthermore, the A5+ has a greater range of volumes than the A5. For example, with the A5, I couldn't max out my source volume (my computer) because if I did, I would have to barely turn up the A5's volume because it'd be too loud. But if I did that, then the A5's sound would be unbalanced b/c the A5's volume was too low. As a result, I always had to put the source volume at around the middle and turn up the A5's volume. But with the A5+, I can max out my source volume and also turn up the A5+ volume just a little bit and get the perfect volume I want.
The remote on the new A5+ is also godsend. It is sooo nice. Seriously, I was in the same shoe as you OP. I really wanted to like the A5's because they sounded great, but I couldn't because of the stupid hissing and popping noise. But with the A5+, I can't find any flaws. It again is the A5's made to perfection. If you have some extra money to spare, I'd highly recommend the A5+!