Is it possible to have perfect room, treated or not? My understanding is that, at the very least, it's almost impossible to treat a room for low frequencies completely. One may have an excellent room that sounds very good but that doesn't mean there isn't room for improvement. DSP can implement functions that simply are not possible with room treatments, such as variable phase correction across the frequency range.
I implement DSP in my two channel system (via MiniDSP hardware and Dirac Live software). If there is any degradation in sound, as some claim, I don't hear it and the benefits achieved through DSP room correction far outweigh any. For me, in my space (partially treated with absorption panels on key surfaces, 14x24'), my system went from sounding not right, fatiguing, uneven bass response, to one I look forward to listening to every day. I'm sure it's not perfect, but I couldn't tell you what's wrong with it.