I would totally agree with mahler123. The actual DAC chip used has very little to do with the overall sound quality. Although, I have heard that the Sabre DAC chip is actually very picky and can be challenging to implement properly. The biggest parts of a DAC sound quality are the power supply (enormously important!) and the I/V and LPF circuits (which op amp / discrete? / Class A?).
Going back to the original question - Is it worth it to get an integrated with a built-in DAC. The power amp section is probably going to have it's own power supply, since it will typically operate at something like 50V or 63V DC with high current. However, the preamp/DAC section has these stages:
digital receiver (usually 3.3V, sometimes 5V)
DAC chip (typically 3.3 - 5V)
I/V (voltage to current) conversion circuit (anywhere from +9V to +/-15V)
LPF (possibly) (anywhere from +9V to +/-15V)
preamp output buffer stage (anywhere from +9V to +/-15V)
On an integrated amp, all the low voltage circuits are going to be using a shared power supply because there is limited space and there's no room to space out different power supply sections for the different DAC/preamp stages(capacitor bank / regulator / any post-regulator caps). The 3.3/5V regulators are probably going to be tapped on the +15V power supply line (example). This means that when a waveform hits (such as a drummer hitting a snare) the DAC chip, I/V, LPF and preamp buffer are all going to try to draw that voltage/current from the +15V power supply line. If the power supply is not beefy enough (and it typically isn't), then the power of the waveform can suffer and this can translate into a weaker sound that lacks punch/authority. It may also lack clarity.
I would not focus much on the future and new formats/technology. The most important factor is the quality of the analog audio circuits themselves. I have had a old Krell HTS 7.1 from 2001 that pretty much kicked the crap out of a LOT of new stuff (even though I could not play hi-res audio or bluray formats). Even though the new technology promised better sound, my old Krell still beat it with lo-res data. The Krell had all individual power supply sections for digital / DAC / Analog sections.
Buying an Integrated with a built-in DAC is definitely very convenient and this may fit your requirements. If you're after sound quality, it's best to use a separate DAC. That allows the preamp section in the Integrated to use it's own isolated power supply.
