Ok I see it’s the Little Dot II and III that have pre-outs. The best thing to do would probably be to upgrade to a headphone preamp combo unit and then go to a power amp. If you like the Little Dot I the II or II would make sense but there are lots of options. Initially you can just run with amp and use software volume controls.
As far as amps I would advise against going with anything “old vintage”, I would say nothing older than 25 years. Rotel, Adcom, and NAD make some really nice fairly compact power amps that would work well, about the same price as a receiver and much better quality.
I would say you probably want about 15-50 watts if you are going to be using them on your desktop nearfield, my GFA-535 II is 50 watts into 8ohms. A T-amp might ok but they are a bit short on power but I’m not sure how efficient the ZA 5.2 is and T-amps are bit short on power. Not only that but their distortion quickly rises when you start pushing them.
As to the cabinets, personally I like a wood baffle (front) but if you like a matte black baffle painting it is really the only way to get that look. Matte black is probably the easiest finishes you can do, which is why you see it so often. Is there a reason you are opposed to it?
FYI, I have those very 0.25cuF Dayton cabinets you linked to (in cherry too!), I’ll be making a solid wood baffle for mine though, most likely maple. The quality is really pretty impressive, I would defiantly say they are worth it if you can’t / don’t want to build your own cabinets; building curved cabinets is quite the undertaking.