I think that person Wayne is talking about is yours truly
There are TWO things in my opinion that make the xr series amps world class. First, the mods. The unit is fine by itself, but it really is a case where you get what you pay for. The level of detail is there in the stock unit that requires a large investment otherwise, but soundstage is just not IMHO. You will be much happier sinking money into the unit with mods.
2. Power conditioning, specifically a balanced power conditioner which tend to not limit dynamics. I used a BPT unit on the stock unit before mods and it was night and day sound-wise. While I always thought the stock unit presented a black background, something about it made it seem hazy if that makes sense, almost like some white noise was there that shouldn't have been, electric if you will. The BPT solved this for me. I still have the bpt, and I believe Wayne uses an equi=tech unit on his fwiw.
In summary, the xr series amps are great for the money. No where else can you drop three bills and get that level of perfomance from a stock unit. However, there is a lot of potential in the unit just waiting to be released, but as with most things, this requires an investment.
Spend the money if you have it, if not, listen to what Wayne was saying about metal and all of the aforementioned comments.
Daryan