Good to have a plan in mind, but take one step at a time. Speakers is the best first step IMO. A synergistic amp is the best second step. Wait for break-in to occur (hundreds of hours), then decide on the next step.
DACs are hard to invest heavily into as the value of new products keeps going up and up.
IMO any Omega speaker would totally outclass a cheap subwoofer (like the Pioneer, not that its not 'nice' for the price, but come on it was designed to pair with $130/pair speakers). If you want the bottom 1 - 2 octaves, without one note boom or sluggish performance, you'll have to ante up for a good sub. Most recommend sealed for music (tighter, better defined bass) versus ported (deeper, louder) for the HT crowd. A good example is the $650 USD SVS SB12-NSD: 30 - 250 Hz, 12 inch high quality driver, 14 inch cube, 400 watt amp, DSP (digital signal processing, customized to the cabinet to optimize performance). Another good example, but they've been out of stock, is Epic Legend: opposing 12 inch drivers, pricing uncertain. Bottom octave bass is foundational to the overall musical experience and can actually improve imaging, but beware that deep bass can bring all sorts of other challenges (upset neighbors, rattles, uneven in-room frequency response) that can cost thousands to properly resolve.
With the right room (size/shape) and speaker/listening positions room treatments may not be needed (they have negligible benefits in my single driver/proper room system).
