Hi Spanky,

Yeah, as everyone has said. Companies make systems with higher THD because they are cheaper to build and can be sold cheaper. The distortion does increase with volume.
Question: How does your system sound to you at the volumes you want to listen at? If the answer is that you can hear the distortion, or that you wish you could turn it up more, then your system is not doing what you want. But if you upgrade your $150 system for another $150 (or even $200) system, there won't be a lot of improvement. Quality costs money. In my opinion, you would have to double the cost for each 10% increase in quality. You're better off by saving up for something that will blow your socks off, than to keep blowing your money on small changes that just leave you just as unsatisfied as you already are.