Hello, the short answer IMHO is YES! But I can do even better to answer this!
Try different programs on your Mac like Amarra, Pure Music, Audirvana, Fidelia and others. In the order listed, I have tried all of these and find some very interesting results in terms of the sonic signature.
With the Audirvana program, there is a Mode switch (Mode 1 or 2) that allows selection of Transparency or Smoothness that really has a startling effect. The Transparency setting is a To Die For setting in my opinion for really well recorded tracks. The Pure Music allows to Upsample even Internet Radio (with Premium accounts like SKY.FM, Pandora and JAZZradio) that is a distinct improvement and sometimes 128K AAC is good enough for hours of backgroung listening to music you may not have as CDs.
I am using 2X Upsampling whenever possible and for the record, I have a Mac Mini USB connected to my NAD C390DD but also have an AES/EBU and Optical connection from my Logitech Transporter to the NAD as well as a Mark Levinson No.39 Transport to the NAD that I use for comparisons. I have 1900+ CDs (Classical, Jazz and Rock) AIFF ripped to a 2TB FireWire connected drive to the Mini. My speakers are 20 year old (mint) Aerial Acoustics 10Ts that I simply cannot live without! And by the way, cabling does have a profound influence on the sonic character as well!
I truly believe I hear a distinct improvemt using Upsampling but as I said even more with the selection of which UpSampler code (Pure Music's own filter versus the MIT created iZotope SRC which has claims of being the most Transparent) can only be demostrated to believe!
We are getting to the stage where we will be able (and now are) able to dial up the sonic signature desired for any music track equivalent to changing the entire system components for their specific sonic signature characteristics!!! Like what a Wadia, Mark Levinson and Krell for example sound like. Of course, a flat and detailed capable system and the flat room response is required to do this. I have my room response compensated for using the Room EQ capabilities of the NAD C390DD as assited by my BSR 4000Xr Real Time Analysis component. Amazing how the bass is cleaned up using this NAD filterring capability.
These are definetely FUN times with plenty of future opportunities on the Horizon.
BTW -- 2X Upsampling uses much less computation and really doesn't destroy the music in my opinion.
Have Fun and enjoy the High Tech side of being an Audiophile (Digital Rules!),
Laurier
Izotope SRC