I kind of like HQPlayer myself, it uses your CPU horsepower instead of the chip inside your dac to do the music upsampling with much heavier digital filters.
For me the differences are subtle but nice, for 44.1khz content digital filters can have quite an impact as the nyquist frequency is so close to the audio band.
But don't believe my claims, you can listen for yourself! It has a free trial mode with the only limitation that it has to be restarted every 30 minutes.