Any worth improvements with some cheap amps like the magni or the vali? (Not going to buy them, just for science)

Nope?

Will you be modding these?

Vali = slight hiss. bassy, warm, full bodied bloomy sound. maybe a bit too much.
Magni = actually pretty good.

This is a pretty darn good starter headphone for $70.
BTW, the Senn HD558 will fit inside the Takstar box. It's tight fit, but can be improved if you are willing to cut small parts of the foam out.

I hope this thread necromancy isn't frowned upon, but it's really interesting to see these measurements. I think the roll off (or lack thereof) in the 10kHz+ treble is really quite impressive for a headphone that doesn't claim to use any exotic materials or technology. I was listening to the Takstar Pro 80 today to compare it against my shiny new AKG K553 and I was really reminded again just how great a headphone it is for the price. It's a little depressing that more people don't mention it.

It's my second unit after my first unit was eaten by an amplifier, and it seems that Takstar has made some revisions. My new unit has a straight cable instead of the previous coiled cable. Build quality seems to have improved slightly too, because my new unit is actually symmetrical instead of slightly bent like my old one. I wonder if a new unit would measure any better?

You know, I got a pair of these a while back. I should get measurements posted soon. I took a brief peek at measurements but didn't save results. Subjectively and as measured, they are incredibly U-shaped. Actually, ¯¯\__/¯¯ shaped is a better way to put it. Thankfully, the bass is more or less in-line with the treble, so it's not too displeasing to listen to. I won't bitch for the price, and I bet they can be tuned up nicely with mods. Build quality and included box alone almost make it worth the price.