Modded Players Bias in Listening

I read so many posts from people who love their newly modded CD players, whatever make/mod.

Here's the question - anyone listen to two stock players side by side of the same make, ship one off for mod, and then listen to the two again? I'm not speaking in absolutes, but to some degree when you lose a piece of gear for several weeks AND fork over 500-2000 bucks for the mod, I would think it possible for some bias to creep into the regular human's evaluation. But I am interested in hearing anyone's tales of A/B as mentioned above.
I did this after the fact with my Sony SCD 777ES a few years ago after I had Jerry Ozment modify it to bypass the Sony analog stage with his tubed Audio Logic analog stage. A friend of mine had a stock 777ES for which he was considering modifications, so I brought mine over and we compared the two. I'm was sort of relieved to find that the improvements were quite audible to all of us who were there, right from the first bar of music, even though his player was fully warmed up and mine had only a half hour warmup. I had always felt the improvement in sound was significant compared with other Sony SACD players of that type I'd heard, but truthfully wasn't sure about the magnitude of the improvement until I did the comparison in the same system.
Your question was specific to CDPs, but I did have an opportunity to compare a Counterpoint SA220 amp, modified to a Premium NP220 by Mike Elliott, to the stock SA220. I owned both at the same time, and was able to A/B compare the two. The modded amp was a significant and noticeable improvement over the stock amp in all aspects.

But, that being said, I tend to agree that there may be a lot of "rationalization" when one pays big bucks for a mod.
I would imagine that typically a modded player will almost always perform better in certain parameters than its stock counterpart. I've not heard too many claims otherwise.
I was very high on modded cd players (had the fully decked out Ah! Njoe Tjoeb) until I compared it to the stock Rega Planet 2000. In my system, the Planet handily outperformed the modified Marantz. I was shocked/horrified to see that the tube player was bested in resolution and warmth by a solid state unit! Before I purchased, I posed the question on an Agon thread re what unit would be a step up and several persons recommended the Planet. I would suggest you do the same before you jump for a modded player. It is entirely possible that a stock player will be better for you than modded players.
Taught me an important lesson. Supercharging a lower end player doesn't really get you a high end player.(Not suggesting the Planet 2k is a high end player, but to me was a step above the Ah!)Tremendous claims are made of these modded units competing with stock players 3 or even four times the price. Don't uncritically believe all the hype. Let your ears decide. They may sound better in significant areas of the listening experience, but not necessarily better overall.
When I switched, the used prices of the two pieces were approx. the same, so the upgrade was quite painless.
Sadly (or happily, if you've got the time and cash to have an extra unit sitting around for comparison) you simply have to do your own shoot out with your own components to know for sure. Too many variables otherwise. imho

Good advice to keep in mind. There are some interesting debates on the Jolida JD-100 that shed some light on this topic as well. I can certainly understand someone wanting what essentially is a "custom" unit to gain better performance over the stock version.

I recently have heard the stock and modded versions of the Jolida (two different levels of mods from different sources). The stock unit has a warm sound that is somewhat lacking in detail, yet very good considering the cost. The first modded version was basically a retube and some sound dampening. This was a nice mod in my opinion as it cleaned up some of the sound and added additional warmth and detail (not much, but enough to notice). The second mod was essentially one of those "makeover" mods that you see advertised. While there was a definite upgrade in sound quality, especially in detail, I would have to agree with those who say that this type of mod results in a sound that was not the initial intent of the JD-100 design. Considering the cost of the mod, one could actually go out and buy a stock player that would provide equivalent if not better sound. In the case of the Jolida, and I'll venture to say other mods, sometimes less is more.

As you say, supercharging a low-end player does not get you a high end player. It may get you the sound you are after, but perhaps another stock unit would have accomplished the same thing.
>>perhaps another stock unit would have accomplished the same thing.<<

When buying modded equipment one must consider the base unit and mods performed. I recently heard a stock 7 year old Sony XA7ES (available used on Agon for under $1000) alongside a level one modded Jolida JD-100 and the Sony destroyed it.
Jimmy,I am fortunate to be able to listen to the stock
DVP 9000ES,after my 9000es was mod,the difference is
huge,the stock Sony is also lean sounding cdp,a bit
brighter, bass is fair,soundstage is acceptable,vocal
is good.My Sony9000esMod, it has good layering, good
extension, excellent dynamic micro and macro,it has
rich full sounding, and natural,bass is five times better.
Its quicker, with good transient.And the strength of
this player is very musical. Thanks

I'm not surprised at the result of your comparison.
Bias, bias? after spending good money with a mod man? It would be silly to say how good it is if it is'nt. The only bias one would then have would be against the modder. A well experienced music lover, and ligitimate audiophile, should be able to tell good, and undeniable improvement when he hears it.But beauty is in the ear of the (beholder) hearer. no rudeness intended.