Jakby ktoś miał wątpliwości co do używania AUX i DAC'a I think you're splitting hairs when comparing one DAC vs another, especially in a car. The real degradation happens after the conversion to analog. Worst case is AUX in of the OEM HU, stay away from that at all costs. Very good results can be achieved by simply hooking-up a USB thumb or HDD to the USB port. The absolute cleanest signal path, without changing the OEM HU, is to play either lossless files from USB, or Audio CD, using the MOST bus to transfer the signal to the trunk (you would need to re-code to top-Hifi), and then using a Mobridge pre-amp to convert to toslink, and then a processor with digital inputs, like the Bit10 to convert to RCA, or an amp that takes toslink. But once you turn on the engine, or the A/C, or the wind blows, all that pureness goes right out of the window.