alpine iva d105e and pxa h701

hi. i have an alpine dva 105e(with built in dolby digital 5.1 decoder, 6 rca pre out.) connected to the 701 using an optical cable and the ainet cable. i am using it as a 5.1 channel audio set up for the 3 memory settings and as stereo for the other 3 memory settings. the head unit's DAC is 24bit as indicated and plays dvd audio.QUESTION: to maximize my 24 bit cds, is is better to use the rca outs of the head and just get an audio control equalizer or just stick with the 701. also, the head unit manual indicates that using the optical output switched to bitsteam,in a 24 bit cd , only 16 bit with a sampling rate of 44.1khz is output throu the optical wire. is this true? does the 701 have 24 bit dac?