Ways to improve DAC performance???

You are far better saving for a High quality dac that has DSD
Which is the hot new ticket. Why not buy a program for ripping and converting files like DB power amp which is very accurate to a external 2T drive, then to a Auraliti player then you can sit on your IPhone or IPad
And direct and play Wav files or flac files right from your chair even upstairs,you download a Mpad app and you are golden.your whole library at your disposal.
I would also like to mention your Usb cable from a seperate hard drive, as well as USB cable is Very important , bits are not just bits the timing
And accuracy is very important.i use Wire World
Silverstarlight , and Platinum Starlight Digital cables with Excellent results.

Install Audirvana - it bypasses the apple processing and delivers the raw data from the file to the dac. - it can also play flac if you desire.

It pre-loads tracks - so there is less of an issue using wireless, which can lead to dropouts with itunes alone

It also integrates with iTunes, which I use with a droid app called Retune to control from my tablet

I was very surprised at the difference it made - better imaging and dynamics

Get a half decent cable - I use DH Labs for USB and optical- they've so far proved to be better than other brands I have tried - like Chord. They do affect the sound, because some cables drop data when streaming and the dac just fills in the missing data best it can.

Also, make sure you either backup your tunes frequently - or get a drive (NAS or usb) with dual drives that support RAID - I've now reloaded my cd's a couple of times due to hard disk failure

Hope this helps

If you are ripping CD's, then use XLD rather than iTunes.

Players like Audirvana, Amarra and Pure Music will improve the playback quality over iTunes.

The biggest improvement you can make is to use either a reclocker from your MacBook or even better, use a good USB converter with separate power supply. This locates the MASTER CLOCK outside of the computer and with a good clock and power supply. Buying a more expensive DAC and still driving it directly from a MacBook will not make a big difference. Fix the digital source jitter first. BTW, I use a 2009 Mac Mini with external Hynes supply as my reference at home and at shows.

Also, you will need good USB cable, such as Audioquest Coffee or even better Diamond and you will need a good digital coax, such as my $250 BNC-BNC with adapters. Unbeaten so far.

Steve N.
Empirical Audio

You may want to consider foregoing a usb cable once you make the move to usb.

Discussed here:
https://sites.google.com/site/hifacemods/home-1/announcements/improvingusb

I went that route with no usb cable and have experienced improvements in the sound I'm getting.

even better-dont use usb at all! get a soundcard. why change sound to usb than back when you can just get spdif from your puter with a good soundcard? I have done that, saved $2,000 on a usb converter-have better sound, and have NEVER looked back!