Do I even need a dedicated stereo preamp?

The suggestion above for the Schiit is a good one. It’s offered with IOS app remote control and has tube output, SS output and no gain output.

I like that it has both tube and SS, but unfortunately I only have android devices in the house. They say they are working on it (no idea when that was stated). 

Decoupling those Tektons from the floor and proper placement will yield amazing results.

A few months after I purchased my Tekton's I put AUVA 100 feet on them. Big improvement on my suspended wood floors. I also spent hours in REW taking measurement after measurement. I moved them around probably over 20 times. Once I found the most optimal place for them within aesthetic reasons and of course WAF, I used a laser measure to ensure they are symmetrical in my room. I have first reflection panels on the left wall and a heavy curtain on the right wall along with a big couch and a large rug. Room treatment is nearly perfect. I think as diffuser on the rear wall would be nice, but the panels, curtain and rug make a huge difference. 

The slightly warm Kara F is not as good as the Serene but cost $700 and I am enjoying the heck out of it with the Schiit Wotan amp and Magnepan Mini panels. I did not want to spend more on the preamp than the cost of the amp and Mini. It was a good move in retrospect. The HPA4 in place of the Kara improves the system but the Kara is not that far behind. This is the new version of the Kara.

That's good to hear. That price is more manageable. 

If you’re ok with SS, I’ve had an SPL Elector for a few years now. It just keeps surprising me with whatever I do up the chain. For the money, it scales like you wouldn’t believe. Spacious, detailed, balanced, neutral (mostly), refined, super clear but fluid. Almost tubey? But no tubes. Don’t plan on replacing it any time soon! 
Only caveat is the casework could be more solid. Would recommend using the Stack audio auva’s underneath one 👍🏼
 

Sell the A6, buy an A8 or A10. You will get a better DAC, a balanced pre with a resistor ladder volume control all using the same app you use now. My A8 sounds great.

Good advice here. Schiit was my gateway drug for preamps, I had the Freya+, and it was a big step up from the preamp in my NAD integrated. I upgraded from that to the Benchmark, more improvement in details, but a bit on the sterile side over time. Great preamp for low volume listening. Unless you want to mess with tubes, I would go with the Kara.