What is the SACD Mod business all about?

OEM aren't interested in getting the ultimate best possible sound possible from their equipment besides there's not a big market for the ultimate sound quality so that's why there are several companies offering modifications.

While I haven't had any modifications done to my SACD player, I can understand why someone else might want to. Almost all consumer electronics come to market with a varying number of compromises which allow them to be sold at the prices we see. The Mod industry exists to correct as many of these compromises as they deem appropriate. Most offer tiered modifications so that they have something to offer at a variety of price points.
By replacing parts with similar items of a higher quality they can often improve a product so that its performance exceeds its cost relative to other items available in the market.
I am perfectly happy with my current CD/DVD/SACD player (a budget Sony model), but it's nice to know that if I ever stop being satisfied with it that I have the option of turning it over to someone that can improve it for me.
There is an element of faith and trust involved in the process and proper research can help you decide if it is the right thing for you.

I liken an audiophile buying an SACD player, which is not TOTL, and then contemplating modifications ... to an avid bicyclist buying a name brand bicycle, which is not TOTL. If you are really into riding and buy an inexpensive name brand bike ... you wind up upgrading just about all the components (derailleurs, shifters, pedals, saddle, etc.). anyway. And with many bicycle manufacturers, the frame does not necessarily change as you go up the line. After 20 years of buying mid-line Univega and Giant bicycles and then modding the hell out of them, I bought a Cannondale ... it came with most of the mods that I wanted anyway.

In general, I believe that it pays to buy the most expensive component that you and/or your plastic can afford and then, not getting too hung up about all the mods. My take on mods is that the changes are subtle, when performed on more expensive components.

As for putting your money into maxing redbook CD performance, that makes sense too. A great source can make a great system. I got into SACDs and purchased a SONY SCD555 ES, because I needed a new CD player. At the time, it was SONY's third most expensive CD and/or SACD player. It was the most that I spent on a component (paid $1100, its list was $1700). The only upgrade that I would like to do is replace the power cord, but since the power cord is not detachable ... it is one less thing to obsess about.

Regards, Rich