Next best exponential DAC quality level?

I'd say you learned an important lesson about DACs, price doesn't = performance. You could spend 10x as much and still not hear differences unless the DAC has been purposely built to have a sound signature.

Once they hit a certain SINAD all DACs do sound basically the same in they don’t contribute to the overall distortion of the system. If in doubt then do a few ABX tests.

I’m always amazed how anyone can hear differences in DACS where even lousy ones will have a SINAD of -85db with background noise in most homes around 30db and the distortion from even great speakers can reach 1% . It’s a miracle on par with Stevie Wonder regaining eyesight, but to each his own.

I didn't say there's no difference in sound quality. I said once a DAC has reached a certain point they will basically sound the same. For instance a MHTD Pagoda injects enough distortion to have a sound signature. The problem with the DACs all sound different crowd is they have never controlled for bias or level matched properly. I have listened to a lot of DACs , some fairly cheap,  some expensive and one thing I've learned over the years is price does not necessarily equal performance. 

 That’s like saying once amps reach a certain point there’s no difference.

Once they do, there isn't. 

Addressing the OP. I doubt you would find anything "better" than the SMSL  if it has the features you want and you're looking for a DAC that's not going to add coloration. If you're thinking warranty purposes and the hassle of shipping overseas there are US companies like Benchmark,  Bel Canto, Schiit etc. Don't get sucked into the rabbit hole of more expensive = better in DACs no matter what anyone tells you, even me. Find out for yourself, while not perfect try to compare them blind and level matched if possible or at least level matched. 

Because DACs measurements are different doesn't mean you can hear differences or pick which is which in blind testing. Being more realistic I would say some $200 DACs would be hard if not impossible to guess better than chance from some $5000 ones. 

What exactly can DACs do within the audio reproduction and human hearing bandwidth that can't be measured? I'd be interested in knowing.