I have both the Oppo BDP-103 and the BDP-105D and have used both in the same system. Substituting the 105D for the 103 was a definite improvement in sound quality to my ears. They do use different DACs. The 105D uses the ESS Sabre32 32-bit DAC (ES9018), the BDP-103 uses a 24-bit Cirrus Logic DAC (CS4382A). My Oppos, by the way, are used in systems with Maggies (1.7i or 3.7i), if that has any import for the OP.
LarryRS
LarryRS