In my opinion because you have the speaker setup already, the DAC is the best option. But it also depends on the speakers you have, so they can take advantage of the DAC. Also I am not an expert on DAC, so for 90 euro I don't know what decent DAC you could buy. I heard the AudioEngine D1 is a good one, but it's a bit out of your price range and it doesn't include amp I think.