I humbly submit the Ember as a recommendation. Yeah I know it's far under your budget, but it's what I have experience pairing the 560 with. I found it better at softening those sharp frequencies (I hope I'm thinking of the same problem areas as you) than the Asgard 2, which seemed like a pretty good amp already.
Of course at your budget, you could start looking at the EC Black Widow. If I had your budget, I know I would.

Anyone here owns or demoed the Custom Art Harmony 8 or the H8 Pro?  They are on Massdrop for under $800.  Would either be similar in signature to a RE400 or something like a HD600/650?  Or should I wait for a UERM drop?

Guys I need guidence to my decision easier and to feel better about myself!
I wanna get rid of my LCD-3Fs, im bored of Audeze's sound and comfort.
Hifiman is in my eyes, HE-1000 or HE-6 I guess... However im not too found of modding in general, and my first impression of the HE-1000 was that their bass might not satisfy me.

I listen to 90% electronic music, so a hard hitting kick drum is importent. Clearity and airness is also importent.

Here's the dilemma:
Return the LCD-3F to the dealer (its amazing that the dealer will allow this as I bought the headphones 3 months ago) and pay 1300 bucks to get the HE-1000 to pair it with my current amp, a Mjolnir. (1300 is bcuz prices are higher in my country).

Or :
Sell LCD-3F for around 1900USD
Buy HE-6 for 1250 (I cant find any used in my country...)
Sell Mjolnir for around 450
Use whats left, hopefully 1150 + my wallet 1300 to get an amp for them.
To give you an idea, a Ragnarok costs 1950 here.

And ofcourse, I always try to save up money, but ive just moved into the city (which is expensive...) so im kinda broke atm

Or should I look at something else?

I dont like closed headphones, cause they sound closed

Aside from physical appearance, TH900 is not a closed headphone.