You may want to seriously consider continuing to enjoy your (really quite good) HD58X just a little longer to save up the extra for the Koss ESP-95X. I think there's a discount code in the deals thread that let you buy these for $400 (which I think is a great value EDIT: when compared to other over-ears in the same price range. There are absolutely cheaper headphones which provide better value per dollar if that's your priority).
The sound quality is remarkable. Available measurements (of either the ESP-95X or the ESP-950 from which they are derived) show very low distortion and a relatively neutral, inoffensive frequency response. I use a slight low-bass shelf (roughly equating to +5dB under 50hz) based on measurements performed by oratory1990, but otherwise no EQ or modifications.
In my subjective opinion they truly outclass any other headphone I've owned (AKG K240, AKG K702, Fostex T50RP MKIII, Sennheiser HD650) in both sound and comfort. They are about as open as a headphone can be. It's easy to converse with someone in the room, or hear the doorbell without taking them off. It's also easy for others in the room to hear what you're listening to if the volume is turned up a bit.
There are three common "complaints" you'll see about these if you start doing your research.
First, ignore reports of them feeling "poorly made" or "chintzy". They're certainly surprisingly lightweight (largely due to the extremely open enclosures and the electrostat driver), but no more "flimsy" than other headphones I've handled at similar price points. I use them daily at my desk and have zero concerns about longevity. Notice the lack of reports of broken headsets.
The second is complaints about the split volume knob of the E90X energizer. While I admit that it demands a little more attention when adjusting the volume to ensure the L/R levels are matched than is typical on a headphone amplifier, once again I think the issue is overblown. Once I got used to it, I had no issues adjusting the volume with both knobs simultaneously. I also appreciate the additional 'balance' capability this split knob provides. Personally, I no longer use the volume on the energizer. I now use the digital volume control on my DAC, and have the E90X set to a level that corresponds with the loudest level I'll ever listen at when the DAC is at -0.0dB. In your case, you could use the JDS Atom as a preamp and control volume with the nice large knob it has.
Third, the "crackling" or "popping" noises many users report. This one I can't dismiss so easily. Electrostatic drivers certainly seem to have their own quirks. I bought my ESP-95X pre-owned off eBay. I had read all about these noises from many places online prior to receiving the headphones. During the first few days of use, there was nothing at all like this. Later on, I started to hear some minor 'electrical discharge like noise' in the right side. Fearing the worst, I contacted Koss customer support and was immediately sent instructions to return them for warranty service. I never got around to sending them in, and about a week later I realized I was no longer hearing the noise. It was just gone. Is this a design issue, quality control, unavoidable quirk of electrostats, a break in period, or just a fluke? I really don't know. I do know that for me, the problem has completely disappeared and if it comes back I have 100% confidence that Koss will address it in a timely and professional manner.
I figure it seems like I'm shilling pretty hard for these, but honestly I'm just very pleased with them. I was looking for my "end game", and was really keen on the HD800S but had deep reservations about the cost/benefit. After looking at a ton of FR and distortion charts, I decided to take a chance on the Koss. I bought them figuring if I wasn't impressed I could sell them and recoup nearly 100% of my cost, then buy the Sennheisers. After using the ESP-95X for about two months now, I'm convinced that they're here to stay as my "daily driver".
I will also not be replacing the pads (the vesper pads seem heavier, bulkier, and less breathable than the stock pads), or fussing around with Stax energizers (which have never been properly tested or had their effect on the FR measured).