Wow, that's a terrific response! Thank you!Gotcha. That is tempting. My advice is if you really, really want to try the 660s now sounds like a great time to get them with the refurbished deal. Sometimes you get an itch and you just have to scratch it! Lol! Also if you really want to consolidate the 660s is a logical choice.
Having said all of that with your use being 70/30 gaming to music another option you might want to consider is holding on to the 58Xs and 6XXs. Continue using the 58X for gaming and get an OTL tube amp to run with the 6XX for music. The 6XX/650 really come alive with an OTL tube amp. The absolute best I've heard any of the 600 family of cans sound is the 6XX with an OTL tube amp (in my case Schiit Valhalla). I'm not sure if the 660s is going to be that much better for gaming then the 58X (and quite honestly the 58X sounds close to the 660s for music with some genres like metal and classic rock, where the 660s really starts to separate from the 58X is with jazz, classical, folk, and acoustical). With the addition of an OTL tube amp with the 6XX you would have one setup optimized for music and still have the 58X which is great for gaming.
Many people don't consider the 660s as an upgrade to the 6XX as much as just another option with different tuning. I personally think it's the best all-around phone in the 600 family but the differences are not huge over the others. So that's a really long winded way of saying if you really want to try the 660s go for it! I don't think you will be disappointed but you may want to consider keeping what you have and adding equipment to optimize what you have. Either way I think you'll be happy.
I actually like the 58x the most of any headphone I've tried, weirdly enough. The 660s sounding similar to the 58x is actually appealing to me. In the genres you mentioned that set the 660s apart, what specifically makes it better?
I'm not sure I can justify more source gear, as if anything I'm trying to pare down my audio collection lol. Though if the 660s is more just another 6 series flavor rather than something clearly different, I may be better off keeping what I have.
I also own the 560s and pc38x. I feel like having all 4 (those two plus the 58x and 6xx) is too much, but I have trouble picking one up sell lol. The pc38x is great for console usage and playing multiplayer games on PC with friends. The 560s is TERRIFIC and scratches that wide soundstage, neutral itch. The 58x and 6xx are probably redundant, but when I compare both I can't seem to pick one to get rid of lol, love em both.
For pure music listening, the 6xx is just incredible. Especially on high gain on the Hel, even though I can't go past like 8:30am on the dial as it's too loud, the extra power really makes them come alive. Music sound so damn good on them. The 58x though just game way better, punchier and with probably the best imaging I've heard. They clearly don't perform as well technically as the 6xx when I compare back and forth- I never really knew what detail retrieval meant before hearing the 6xx. It just extracts more detail and has more clarity somehow. Still the sound signature of the 58x is pretty much perfect to me.
I do really want to try the 660s though. If it can marry those two in a sense, it would be the perfect headphone to me. If I do pull the trigger I will report back. Thanks again.