Firstly, the roles of a DAC and a preamplifier are different: the former converts digital audio signals to analogue, while the latter boosts (typically weak) signals from a source (a turntable, say) or a DAC before they are fed to a power amplifier or active speakers. However, many dedicated DACs now feature preamp stages and volume-controlled outputs, meaning they can perform both tasks.
That said, the efficiency and effectiveness of a DAC's preamplification duties really will depend on the DAC itself and the rest of the system it's connected to. You may find that the DAC's output signal is too weak, for example, and you won't likely get as much control over level adjustment as you would a separate preamp (or integrated).