I mentioned way back the 3.5 was useless/unservicable...not the tech. But any on-board DAC can bettered by a quality external DAC.
As to the original post, I said adding RC would be a benefit to the HDMI out. No room is perfect.
Most certainly, the speakers are the most important part of a system.
But your economics are off. In today's dollar, $200 spent on a pair of speakers, or even $200/ea is not providing much in upgraded sound.
Its been 40 years, give or take, since I auditioned a pair of speakers at $200/ea I thought were worth buying.
Today, its more like $500~700/ea, minimum, to get something worth keeping.
The XOs I built 12 years ago cost almost that much alone.
But no matter what speakers are being used, Dirac RC can improve the sound.