One mans dirt cheap tweak is a others man arm and leg. Keeping all cable connections clean is great. Getting speaker cables off the floor is one more that i feel helps. Replaceing wall out lets with audio grade plugs is al so great, but not really cheap depending on which one you use. I have found the biggest bang for the buck High Fidelity MC O5s easy to use. May be not dirt cheap but a tweak that delivers a sonic improvement.
enjoy Pete
enjoy Pete