I wanted a Quantum, but couldn't justify the price. It sounds gloriously (that is, in a good way) digital to me and I wouldn't have known the filters are analog (from what I've heard online) if I hadn't read the specs. I would have preferred a cheaper version with wavetables only (with FM capabilities), digital filters only, and more voices. I.e., a knobby updated Blofeld.
Instead I just now purchased a P12 to fill that gap in my repertoire. I needed something glassy/metallic that sits well in the mid range without having to spend time messing with EQ. I had a Montage for a little bit which was full and lush, but found myself preferring the rougher or more characterful/thinner sounds of the DX7. Of course the Montage even has internal EQ and whatnot, but it took up too much space in the mix as is and wasn't as three-dimensional as I'd like. The Curtis filter imo does well with mids and rougher/more old school digital tones. I'm going to be depressed due to my severe impatience if Sequential releases a P12 rev 2 soon, which seems awfully likely all considering. Although if it has the SSI2144, it might be lusher & better if it's your only synth, but lack some of the grit I'm looking for...