Is pre-amp getting killed?

With a properly designed DAC there is really no need for a pre-amp unlesss you need a phono stage, or have a lot of source devices. My DAC has multiple digital inputs and a single analog input. The output of the DAC is touted directly to the amplifier. It works for me. 

Even if you have only digital a preamp is still useful; one way is if you want to run your interconnect cables a long way to the amplifiers (which might be sitting by the speakers with short speaker cables). Many digital products have poor volume controls, so that is another way preamps are still quite useful to obtain better sound!

@erik_squires - What OS are you running on your Raspberry Pi? I have 2 RP3's running an older version of Moode. Doesn't really meet my expectations as a user friendly music server/streamer. A newer version might be better, but a different OS might be an even better answer.

If you don’t need other inputs for other sources, a well designed dac with enough output voltage should be all you need. BUT rare are dacs with a very good sounding preamp function, so comes the time when you can welcome a nice dedicated preamp that will bring your more tone density, dynamics, euphonic coloration, etc.

I do believe the future is a good preamplifier wich includes a dac module inside. We are seeing more integrated with dacs, and more preamps with dacs are to come. Dac miniaturisation is the reason many brands can now include these in preamps. I’m thinking McIntosh , Wadia, Chord, and others.

I totally disagree that a digital passive preamp with dac is as good as a active preamp. Any professional reviewer .myself owned a
Audio store for a number of years an active preamp has much more capacitance ,discreet power supplies and therefore better dynamics, soundstage size and depth and especially when the spl 
levels get loud the performers stay focused and right there ,not thinned out.  A quality preamp normally is at least $3k and up.
the lneartube Audio is an exception to the rule , I would recommendedthe Latest Mojo Audio power supply for that which 
is much better then then their upgraded $600 unit .  The Lascala 
dac is without question more musical then the ps Audio dac. And similar in price, which I owned their latest and sold this spring.
Therasberry pi is good for the monet, but  cannot come close to anything over $1000.  You get what you pay for . I will say one thing IfiAudio  has been producing excellent products 
try their digital usb cable, and usb-3 purifier, and plug in AC purifiers Fantastic give hem 100 hours nothing in the $100 range 
anywhere gives so much for so little $$. And full money back audition.