I just bought my 2010 Bighorn. The sound system is terrible. There is a Pioneer receiver amp, which is probably good, but the little factory speakers are terrible. The amp allows for a number of different sound modes. Some work OK until the volume is raised and others completely distort at any volume.
It took me a while to find out where the sub-woofer is located (behind the fireplace), but it does not sound like it is working. I had an Onyx system in my previous RV and loved it. I just bought an Onyx speaker package from Amazon ($200 off regular price of $499) with 5 speakers and a sub-woofer, but haven't installed it yet. I am waiting for mounting brackets to come from Amazon. My only concern is that the existing wiring is a very small gauage and may be too small to power the new speakers. The new subwoofer is a powered sub. I have determined that Heartland attaches the speaker wiring to the RV, so it will not be possible to replace the old wiring by attaching the new wiring and pulling the old wiring through the RV. I am firstly going to replace the speakers and see what I get for sound before considering any further modifications to the system. Maybe the wiring is OK. If I am not happy with the Pioneer receiver that came with the RV, I did save my Denon from my former home upon becoming a full-timer. I know NOTHING about electronics, so any shared knowledge will be appreciated.
UPDATE (01/30/17). I installed the ONKYO 5.1 speaker system and the sound is AWESOME. The original wiring is sufficient and the Pioneer amp is working perfectly, now that the old and defective Heartland speakers have been removed. The speakers are large and I had to be careful installing them so that the top of the slides would not hit them before dropping into place. Removing the Heartland speakers left large round holes in the ceiling that I did my best to cover with the new speakers. What the speakers did not cover, white duct tape did.