Denon provides a really nice DAC, the DA-300USB ($399). As it also features digital inputs we can feed it with the digital ouput of an audio interface (or even digital output on a mac mini with using the right plug adapter).
There are also other cheaper DACs :
These remain interesting compared to highly priced Apogee audio interface (if we don’t need AD inputs nor pre-amps). However Apogee audio devices provide very low latency, which we have to compare to these USB DACs.
We can also find cheap DIY as digital amplifiers (have to be connected directly to cabs) :