That might be the best solution indeed. I really like this one on classical and acoustic but too bad that my genre variations probably too wide.

Probably not any wider than my genre bandwidth or most others. Is your issue with bad recordings or different genres? If you have bad classical recordings the HD800 will let you know too.

Since I have the Sonett, fortunately I find my HD800 more forgiving for my so-so recordings. I still here they're not good but I still can listen to them. Both with the Metrum ( feeded with 24/88,1 in order to avoid the NOS treble roll-off) and the Beresford Caïman ( a bit less analog sound but more resolving than the Metrum Octave)

Please consider I rarely listen to Rock/Metal & pop music though.

IMO the HD600 associaited wit a good rig for it is a better choice for a blind "safe purchase". unfortunately I don't think the HD600 performs at the HD800 level in many area. You can have your cake and eat. You can't have ultimate perfomance and forgiveness for the flaws of your recordings. it's not really a matter of genre in my experience.

When I had the HD580 ( I didn't own the HD600) I had the Meier Corda Jazz and the HRT Microstreamer as DAC. It was in 2013 and I bought the HD800 a bit later so I didn't invest more time and money in the Rig.  I remember well how I've been wowed when I discovered what the HD580 was capable of from the Meier Corda jazz vs my Previous Aune T1 DAC/AMP .  . It was a really big discovery in small audiophile career.

A few month later, I bought another HD580 and used it With my Old Antique Sound Labs MG Head and a REGA DAC. I even thought to sell the HD800 because of financial difficulties. I thought I could be happy enough with the HD580 and I wouldn't regret so much the 800 . I had even called a buyer so my HD800 was basically sold but I decided to give it a final listen... half an hour later I called the buyer to cancel the sale and the HD580 left the house for a friend. 

A month ago, I thought I was ready to buy HD600 one more time. So I tried it during a meeting on my own HD800 rig but finally I didn't buy it. The gap is bigger now than what I remember... At least to my ears.

genre variance is one of the strangest aspect about the HD800 to an outsider like myself. i've seen posts proclaiming they only sound good with certain genres and on well mastered records, but i've also seen others talk about how amazing they sound on stuff like kpop. without the ability to try it for myself, there's just so much dissonance regarding this headphone that makes it hard to rate it as a safe purchase

You have to be committed to finding a proper rig and upstream for the HD800. It is not conducive to random budget choices as it will let you know those were poor choices and you'll just get fed up, blame the headphone and sell them. Best way is to hear them driven well from good upstream gear first before deciding.

The whole HD800 genre specialty thing is a bunch of crap/BS. That goes back to those poor choices. If you can find our DAC-off spreadsheet/google doc you can get an idea of what music Marv and myself listen to and test with.