debigpr, if I had to guess I would say that you would bore and be just as dissatisfied with whatever speakers you get, unless your loaded and get the best of the best. Then of course everything else in your chain would need to be better .... it's a vicious cycle. Speaker listening can be amazing, I still use my speakers, but the intimacy and details available through headphone listening just can't be duplicated with speakers. Okay, maybe some very high-end speakers will mine the same amount of detail, but get that wallet way open. You mention having the harsh aspects of recordings revealed, that is the hallmark of any headphone/speaker capable of detail retrieval and resolution, they allow you to hear everything, good or bad. I listen to a great deal of musical genres with both 880s and 650s and I do not at all share your experience with the 880, not even close. I think sibilance is a candidate to be "over-reported". Sibilance is natural to one extent or another with the S sound, some female vocalists really make a big s sound, and if they happeen to be close miked during the recording session voila, you have sibilance at the source and of course any good headphone should reveal that. I am not saying that sibilance isn't sometimes enhanced by the headphone, of course that happens, but the sibilance exists in the recording and solid treble extension will bring this out. Some love the hyper-detail portrayl of treble strong headphones, but it is a double edged sword for sure. Same with bass heavy headphones, great for bass, but other detail is obscured.
Sorry for the lecture, but when you post such strong and derogatory comments about the gear people really like they are going to respond, human nature. As I said, I have spent many hours with the 880s and while they aren't perfect, I can agree with very little of what you have said. I will agree that the mids are a tad recessed, but not enough so to be a deficiency, just an area where they could be better. The treble is strong, but not over-bearing or strident, but it does tend toward forward, but that aids in detail and energy so it is a trade off. The better recordings will sound stunning on the 880s, assuming your source is capable, and your source list does seem well regarded, however I have not had the pleasure of hearing any of them myself. You saying the 880 is boomy is very surprising, I can't for the world imagine them as boomy. Just last night I pounded my 880s with plenty of bass, but they never got anywhere near boomy in response. I will say this, the bass was certainly less controlled through my Valhalla than it is with my Auditor, and if I have understood this correctly, a tube amp will rarely be as good as a well designed SS amp at controlling the drivers. I could be misunderstanding that principle, but I thought that was a consensus of the tube amp sound in general, you get the warmth and timbral qualities, but give up some driver control and speed. Anyway, I hope I haven't been harsh, that isn't what I was going for at all, I just felt that I needed to offer another perspective, not saying it is the right perspective at all. I have a lot to learn so I do not pretend I speak the absolute truth. Cheers.