I'd choose based on features since it isn't like comparing for example either of those to an extremely low noise, low distortion amp like a Pass F5 (in which case, if it was a reference system, I'd take the F5; anything less, like a an office desk, only absolutely crappy noise output will outweigh connectivity options on those).
The Topping has USB input to its DAC, that Dayton only has BT. If you plan on using it far from your source unit then it won't matter, but if you want to keep it close to you and your source unit to easily adjust the volume, having USB as a back up might be important.
The Topping only has a preamp output for a subwoofer, the Dayton has an actual third channel for a sub. That might seem like the Dayton ahs the advantage, but in terms of matching to a sub, it isn't. This is because most amps for home use have a built in amp in them anyway, and most don't even have high level inputs (ie the subs that take a signal from the speaker output on integrated amps back when only HT receivers had dedicated subwoofer preamps labelled "LFE" or "low freq effects" in surround sound terminology, ie, the ".1"). This means you have to get a passive subwoofer, which limits your choices among home audio subwoofers. On the flipside, it widens your choices if you can for example DIY the subwoofer to fit in a certain spot, including integrating the enclosure as part of another piece of furniture. Alternately, given the cafe setting, that means lots of food and beverage around, so you might consider a car audio subwoofer that comes in its own box. Given a car environment the driver and wood enclosures might be built to be more resilient to moisture and actual spills, save for how some are covered in carpet that can absorb spills, so if you go with the car sub route try to find a prebuilt or make one wrapped in leather (synthetic if you want it cheap).
That depends on where you live.
If you live outside the US then Polk Audio is more likely to have a dealer in your city or at least the country vs international shipping with Parts Express.
If you're in the US you still have to ship to Parts Express, but any Best Buy/Magnolia or Fry's might have Polk Audio.
If product support was the most important thing, there's a reason why a lot of cafes use Bose.