Well, I should caution you that even with a good DAC (I'm using a Concero), the sound is "softer" with this $120 hybrid amp.
The fantastic bass control that can be had with the DT1350 on good solid state amps, is lost with the Schiit Vali. But the tubey colorations boost the bass energy and bring down the treble a bit, while adding warmth and thickness throughout the FR. There's also a problem with the Vali's tubes having fairly severe microphonics - read all about it on the Vali thread. But for $120, it's a fun little amp that offers an easy way to get that euphonic tube sound. I don't recommend it for planar magnetics, though - the Vali doesn't have enough power, so the dynamics get compressed.
And if you have any recordings that sound bad with analytical amp/headphone combos, the Vali can make that same headphone sound good (with less resolution, of course) - as with the HD800 - an amazingly good pairing.
But seriously, the Vali produces a nice change for DT1350 owners.
Sure. I watched the Vali thread for a while, so I'm up on the sound signature and microphonics. But, it's nice to hear about how it pairs with specific headphones. I also have the DT880 and I've heard good things about it paired with the Vali as well.
As for the 1350, I've found it a little funny with certain amps. I actually love it with my Audinst HUD-mx1, but really don't like it at all when paired with my Asgard 1. I have no idea what it is, but the Asgard just make the 1350s sound a bit lifeless and bland. I really don't have the technical know-how to understand why that may be occuring.