I disagree wholeheartedly. Have had the Argon for a good while now, and although I really enjoy it for its qualities and will definitely keep it, the TH-X00 is a superior headphone for music, with much better resolution. The X00 is probably my favorite headphone ever, because of how goddamn enjoyable it is.
They are both "bass head" headphones in the audophile spectrum, but The Argon is quite a bit bassier than the X00, and also has fantastic soundstage and imaging (on par with the ZMF Ori, another T50RP mod), for a closed back. It's therefore ideal for watching movies or playing video games, making it a more versatile option. The comfort is also quite a bit better.
The Biodyna bass of the TH-X00 is tighter and more detailed than that of the Argon, though (I will most likely never hear a headphone that can match the X00 in this area). The X00's bass remains well-controlled and nimble despite the powerful boost, even with faster and more demanding recordings. This control and detail is interestingly true when comparing all aspects of sound for both headphones. It's especially noticable in midrange, where the X00 has an overall pretty correct timbre with voices appearing overall more in the background in the mix, but more forward than the Argon. The midrange on the Argon feels a bit recessed in comparison, lacking the same amount of detail and resolve. The same is true about channel imbalance and distortion, where the Argon can't completely hide the very hearable imperfections of the T50RP driver.
I still think the Argon is pretty good for music listening, but the X00 is just so much better in general. The X00 easily wins in categories like EDM, Soul and R&B, Rock, etc. Overall, both are fantastic headphones for their price. $450 might seem too much for the X00, but I think Fostex does justice to the price in terms of resolution of the headphone and delivers the performance that one would expect to find for the price. The same is true for its build quality and looks, which is top notch. It's also incredibly easy to drive, and does exceptionally well even out of a smartphone. The Argon (T50RP), on the other hand, needs unreasonable amounts of power.
Your point about the cables is a good one. Which is why I have put my X00 up for sale and ordered a used EMU Teak (a more refined X00) with detachable cables for the same price.
EDIT: I would not recommend Lawton mod, as I believe it screws up the sound. Stick with it as is, out of the box. Adding new pads, or doing mods like Lawton, makes it inferior imo. The TH-X00 wasn't created to be tinkered with, like the T50RP.
EDIT 2: After buying the EMU Teak, it quickly became my daily driver. It takes the X00 and just makes it better. The bass is a bit less and tighter, but still fantastic. Midrange is enhanced and more forward, with details being much clearer in general. The soundstage is also considerably improved. Almost all of this is from the EMU wood, as I noticed a regression in all areas when trying Rosewood or Ebony.
The EMU Teak takes the X00 up a notch, towards something more "reference", while keeping the fun sounding signature. It's more versatile in genres that are generally not considered fun. If there was one headphone I could use for all music purposes (and I listen to virtually all types of genres), it would be the EMU Teak.