@stuff,
"What type of router should I be looking for?"
Start with whatever router your telco gives you. Router is in bottom-half of list of things to optimize later. I currently run a gigabit-ethernet FIOS router that Frontier gave me. If telco makes you pay for a router, compare prices then consult
Archimago’s blog to see what he did. I trust him, on all matters computer audio and more broadly for his objective, clear-headed take on ’audiophile’ industry and equipment rife with snake-oil, bullsh!t and "manufactured consent".
"Just one that I can plug a hard drive into?"
Nope - no stand-alone HD will do that. At minimum must be in an enclosure with network controller, lil’ bitty bus and rudimentary primary controller for I/O to & from disc, across the bus and in/out the network adapter. Like everything else one can spend too much money on such thingz ...
entire companys’ raison détres are stand-alone NAS devices.
You have a PC, with a hard drive, and you will have a router and LAN. So your PC becomes your NAS when you plug it into the router. Any additional stand-alone HD’s will have to plug into the computer (or, the RPi if you go that route). Take it one step at a time (or two), read Archimago, and be ready for lots of unfounded crap about this-n-that you need to buy for ’audiophile’ networked audio.
"...isn’t implementation more important (as important?) as the chip itself?"
Yes, to a degree. DAC chip itself is both indication of level of investment in implementation and a limiting element in overall performance. A crappy analogy: Porsche doesn’t put the VW Touareg engine in the Cayenne SUV, though the two share frame, doors, base electrical etc.
"What about the Katana 1.2?"
Haven’t heard it, don’t need to at this time, so far totally satisfied with ApplePi DAC. Especially see this
informal monthly RPi DAC 'shoot-out' in Hamburg, where ApplePi is consistently a favorite (along with the Katana THD version).