Just finished a pair of speakers for my son's room and they actually sound great

Built a pair for my daughter's room a couple years back, similar look with stained pine and dark fronts, and she still uses them daily for her record player. The thing I learned the hard way was stuffing the boxes too light at first. They sounded thin til I weighed the fill against the internal volume and added more, and suddenly the midrange tightened up. Small tweak, big difference.

For the sub, go slow on the sizing. My first attempt was way oversized for the room and it boomed like crazy in the corner. I ended up building a second smaller enclosure and it blended far better. Placement matters more than raw size in a bedroom, so plan to try a few spots before committing to where it lives.

I used a plate amp with a low pass filter on mine, wich made matching it to the mains dead simple. No fiddling with a seperate crossover, just turn the knob until it sounds right. If you already have an amp with a sub out, that works too, though the plate amp route gives you a phase switch and volume control right on the back.

Also worth doing while the boxes are still open, run the wire before you seal anything up. I had to pull a baffle off mine a week after finishing because I forgot the internal run. Been there with the sketching phase too, graph paper everywhere on my kitchen table for a month straight.

I did a small sub for my nephew's birthday a while back and skipped the passive route entirely. Bolted a plate amp from Parts Express into the back of the cabinet, so the whole thing just needs a line feed from whatever he's playing through. Made placement way easier too, since he ended up tucking it behind his desk instead of right beside the speakers. One thing I'd flag: keep it out of the corner if you can. Mine boomed like crazy until I pulled it about a foot away from the walls and the bass finally evened out. I also went sealed instead of ported after my first attempt with a port had this one-note hump that wore thin fast. Sealed boxes are smaller and more forgiving if your enclosure math is a bit off, which mine always is. I'd sketch the box around the driver you pick rather than the other way round, saved me a rebuild that way. Enjoy the planning stage, half the hobby happens on paper anyway.

Gotta disagree with the weighing-the-fill bit though. Weight tells you nothing on its own, a handful of dense foam can outweigh a big fluffy pile of polyfill and do a completely different job in the box. I chased my tail for weeks on a pair of bookshelves measuring fill by the scale before I realized the type and how loosely it sits matters way more than grams. Pull a wad out, listen, repeat. Your ears will settle it faster than a kitchen scale ever will.