The best tweak is one that is virtually unidentifiable, by that I mean your system just becomes more engaging.
I don't listen to my system I listen to music and actually feel kinda sorry for 'philes that always feel like something is missing in their rig.
Being "sold" tweaks reminds me of "Home Shopping Network"...my better half can watch TV and be made aware that she needs something that she never heard of and didn't realize she wants. Compared to my spending its chump change so it continues with no complaint from me.
Having said all that please tweak to your heart's content.
Freakin' at the tweakers ball,
barts