Sometimes the original design has mistakes, classic example was the Lite DAC-AH. If I remember it was a $2 fix gave a huge SQ improvement. Don't know if it has been corrected this was 3-4 years ago.
I love modding because I think it is the best way to learn how circuits work. The Hiface is another one, unmodded IMO its run of the mill, ~$100 modded it is better than the few $20k transports I've heard. Its amazing how sales/marketing can cut a design to meet the intended market target but thats business.
Its not just commercial products either, I love what Alec C. has done for our DIY community but even his designs can be improved. Modding is natural engineering progression, we call it Continuous Improvement (CI) at work. I despise folks who think stock is superior, thinking the OE engineers did everything perfect, its never the case in the real world . It has been the cause of many arguments I've had with folks on this forum over the years. Sometimes I'm right, sometimes wrong, but that is how CI works.
