For HDMI cables, to be honest, the difference may not be too big. So, a proper shielded HDMI cable should be OK. For speaker, interconnect and powercord should make a lot of difference, esp. powercord. Afterall, pls run-in your machine for sometime, a few hundred hours then to decide what you want to enhance through cables.
And, again, to be honest, high-end machines would be more sensitive to different cables because they can play to the cables' strength. For Low-end ones I don't suggest put too much $$ on, instead, should save $$ to upgrade the machines, more justified.