S2, S4 good.
I stumbled onto a listen last year - had gone to my favorite audioholics emporium looking for something else. They said "come on downstairs and give a listen", and I wound up grinning ear to ear. I'd kinda thought the Sig series was a bit of higher-$$$ hype, but I first heard the S2's that day in the same room w/ all the B&W biggies and they more than held their own. Well, to my ears, that is. You really, really have to audition for your own ears and preferences (unless, of course, you'd prefer to just buy them and send 'em to me! ;~).
I can't comment on really extensive A/B compares w/ other monitor-style speakers - I just haven't had the chance for long term comparisons. I thought the Sigs did fine w/ Mac (and later Anthem) driving them, so I'd guess you'll be just fine w/ your electronics. The little S2's surprised me so much that I probably expected way, way too much more out of the S4s when I later heard those. Both are quite good, I thought the S4s maybe had a bit more bottom, etc. (but that was maybe/probably part expectations & part poor memory - couldn't A/B the 2 & 4) but in the dealer's listening room (not a huge barn) the S2s more than held their own w/o a sub (mostly jazz, not slamming rock for that audition). W/ your DD-15 either should be killers. Good luck!
I stumbled onto a listen last year - had gone to my favorite audioholics emporium looking for something else. They said "come on downstairs and give a listen", and I wound up grinning ear to ear. I'd kinda thought the Sig series was a bit of higher-$$$ hype, but I first heard the S2's that day in the same room w/ all the B&W biggies and they more than held their own. Well, to my ears, that is. You really, really have to audition for your own ears and preferences (unless, of course, you'd prefer to just buy them and send 'em to me! ;~).
I can't comment on really extensive A/B compares w/ other monitor-style speakers - I just haven't had the chance for long term comparisons. I thought the Sigs did fine w/ Mac (and later Anthem) driving them, so I'd guess you'll be just fine w/ your electronics. The little S2's surprised me so much that I probably expected way, way too much more out of the S4s when I later heard those. Both are quite good, I thought the S4s maybe had a bit more bottom, etc. (but that was maybe/probably part expectations & part poor memory - couldn't A/B the 2 & 4) but in the dealer's listening room (not a huge barn) the S2s more than held their own w/o a sub (mostly jazz, not slamming rock for that audition). W/ your DD-15 either should be killers. Good luck!