using a Fiio Q1. i would recommend this. at this price this is hard to beat. Can consider Q1 Mk2, too.

For Amp/DAC; maybe you can check out Fiio Q1 mk2 or Fiio E17k. Also you can check Topping NX series.

K1 doesn't have a battery, so it will draw power from your phone or computer when using it. it is smaller and lighter than Q1, but Q1 can power more power hungry headphone, simply because it has its own power source. As for reliability and durability, both are equal, i think, as both are made mostly out of metal. Although Fiio is china brand, they are quite well regarded in terms of build quality.
depends on your usage. Q1 is a DAC/AMP combo, can connect via USB and 3.5mm
A5 is pure amplifier, people usually use it with a DAP rather than a phone. If chip to chip compare in amplifier department, A5 should be better.
Maybe you can audit it? Starspicker seems to be carrying  both

If you could go over a bit for Q1 mark ii. That would be amazing.