Mahler vs. Strauss

My view of Strauss' music is that it is more of a simplistic, romantic music, that you can easily hum along with, or in you head without, a recording. Much like Tchaikovsky, only more developed and interesting (to me). As such when you are listening to your stereo system you are hearing a focused tune, one that comes from more from the center.

Mahler, not so much. Even though you might be very familiar with it it is not music that lends itself to easy memorization. You may know it well enuf to anticipate what is about to happen but, apart from the performance, you don't walk about humming a tune. In other words it is music that involves you.  Its not background music! The music itself goes from ethereal and quiet to loud and dramatic. Tonal to atonal and back again. Angst and shear beauty alternate.

 Bottom line, as I see it anyway, its not your stereo system so much as it is simply that you are really listening to Mahler more attentively, and quite possibly because of the drama inherent in Mahler's music, more loudly. I can't believe how loud I play the last movement of Mahler 2. :-)

FWIW, a POV from the unwashed. 

I never warmed to Richard Strauss. Even though he stated that he could describe a teaspoon through music, I find it hard to listen to. Add to that fact that he was a deadbeat and anti-Semite, I would rather concentrate on other composers.
Mahler, on the other hand, was a more 'human' composer. His later works are pretty deep, but when you open your mind, they are quite beautiful.
As far as how they reproduce on stereo systems, I would say that is listener dependent.
Bob

Mahler became a quick favorite for me during speaker auditions because of the amount of space in the soundstage -- not sure if that captures what you're hearing, but I can glimpse what makes Mahler's orchestration more demonstrative of a deep or wide soundstage. I've not done more than skim this, but possibly of interest

I have always found  symphonies, regardless of composer, are difficult to reproduces on a home stereo.  Have tended to stay with works ranging from solo, up to quintets.  Personal preference I understand, but for me the listening enjoyment is greater.  

I have not really noticed what you're obviously hearing.  I think newbee's possible explanation makes a lot of sense to me.