Modding CDP's

I'm looking to upgrade my SACD/CD source for a little less harsh sound on old CD's and have been looking at the Marantz SA-11 and noticed the Underwood HiFi modded unit. They state the sound is a tad warmer and more tube like. That might me just what I'm looking for, but I'm confused as to how upgrading components would warm a unit. My first thought is wondering if they are simply dumbing down the sound which gives an apparent tube roundness, but probably yields poor measured performance. Any opinions? And that of course begs the question, is modding a high end treak or just a way to enhance a budget box? FYI I'm currently using the Marantz DV8400, MacC200, Classe monoblocks, wireworld eclipse. I know the conventional wisdom around here is to go with a tube preamp, but my system is on a lot and I don't want to worry about tube life and sound. Thanks
Autoll, having some experience with the Modwright tube output stage that utilizes the 5687 tube type used in the SWL 9.0 SE preamp and Modwright Sony 9000ES/999ES DVD players, I can say that rolling tubes in a Modwright player will change the flavor. For example, TungSol 5687 are very linear, accurate and extended top to bottom. They are Dan Wright's tube of choice as far as I can tell. However, Sylvania GB-5687 tubes add just a touch of warmth and soften some edginess in the upper mids, which I quite like.
I would not upgrade an sa-11. It sounds great as is. Also, to cure your harsh cds is the ability to use differnet switchable filters on the unit.
I found some of my older CD's a bit bright and I suffered from listener fatigue fairly quickly with my Sony 999ES. Got the Dan Wright Modded (tubed) Sony 999ES and couldn't be happier after a brief break in period. The mod does not cure poor recordings, just makes them a little easier to listen to. Well recorded SACD's and CD's sound great.
Keep your marantz?, APL hifi modifies the 5400. may want to E mail Alex and see if the 8400 has the same upgrade capabilities.
Gbm4th, I encourage you to try the Sylvania Gold Brand GB-5687 tubes if you can find a pair. They're relatively inexpensive, but difficult to find.
I have what i concider a fairly revealing SET system and i too was having some issues with listening fatigue.I am a recent owner of the modwright 999ES with about 300 hours on it i would say.I swapped out the stock tubes and put in some GE JAN 7044's as per a fellow audiogoner's recommendation.Definitely made the listening experience better for me.Much better mid presentation and warmer and slightly better imaging i would say in my system which is a horn system.A combination of that swap and me changing 6SN7 tubes in my Wright 3.5 brought it all together for me for now.Can't believe i am satisfied : ) FOR NOW!! argh.
I really couldn't believe the difference just changing out these little tubes can make to the sound.Just goes to show that the units themselves are quite remarkable but finding the tube that brings it all together for YOU can be the quest.Having said that i have never heard the stock Sony 999ES but have owned several other players that i will be posting for sale shortly(no slouches either) and this player outperforms them.Going the modded route has been worth it for me and i have no regrets at this point.
Hope that helps somewhat.
I give up. What are rolling tubes? Thanks all!
"Rolling" is a verb, and is interchangeable with "changing".