Hey chulaivet1966 One question, when you say "When doing your first mix listen through the monitors at a very low volume" do you mean the ones I'll end up buying or do you mean through the hifi speakers I already have in place?
I'm suggesting that you use that as a mixing general rule regardless of the monitors one's using.
Of course, better quality monitors is a plus but not determining for a good final mix.
Again...that's about knowing how your room and monitors translate your recordings.
I'd work toward getting some quality monitors if I were in your position. (that applies to microphone too)
I think you will eventually get weary of average/below average 'hi-fi' monitors because they color the sound by design.
The KRK 5.5" monitors would be far better than any hi-fi speakers.
At normal listening volume I'd say get your vocal at about -10/-12db or so.
Bring up the kick/snare gain to just below the vocals.
Then bring in the lead axe/keys or whatever to about the vocal level.
Then, tastefully bring up the musical condiments (so to speak) being cymbals, percussion, harmonies so they don't sonically (or, obnoxiously) step on the other tracks.
Don't futz with the first mix forever because it will likely be mierda anyway...get used to it.

Think of the first mix as the necessary benchmark from which to start from and listen to on other mediums.
As I say, some may disagree and have different work flows/processes but I'm not chiming in as someone new to this process or mislead you.
I'll guess I'm forgetting something but hope that helps.
EDIT: I'd keep my monitors at the same height and position my self as part of an equilateral triangle.
Should you opt for 5-6" monitors note they are near fields and won't push the same amount of air so maybe 3-4' away would be optimal after some experimentation.
That's my take....carry on.....