First, I'd like to say hi — this is my first post. I'm looking to make my first foray into headphones. As a college student with just a pair of Logitech Z2300 computer speakers, I'm excited for the upgrade to a headphone amp and headphones. I've already purchased a TU-882 amp (I know, I know, tubes, I could probably have gotten a SS with more accurate amplification for cheaper. I thought a kit would be fun though, and it's not OTL) and I'm looking to pair it with the AKG K702. Now, pretty much everywhere else on Head-Fi, I see recommendations for expensive DACs. Some members even suggest spending the majority of one's budget on a fancy DAC, and claim a massive difference in sound quality. However, from my short reading time in Sound Science, I've noticed that there's a massive amount of confirmation bias, wish thinking, and unevidenced poetic ramblings in the audiophile community (lots of parallels to the religious community, actually). So, I'd like to ask here: is there an objective, audible difference between an external DAC and the internal DAC in, say, my iMac? More specifically, has anyone else here with both an iMac (or Mac Mini, MBP, or Airport Express) and a DAC done any blind ABX testing between the onboard DAC in the Apple computer and the external DAC? I'm already out $600 for the headphone and amplifier, and if I can avoid buying another component on my college budget, I will.