some rookie questions

My system Technics SUG700 integrated 70 watts per channel 8 ohms 140watts 4 ohms. Canton 9k reference stand mounted 88dB,JAMO C80 sub,and Marantz cd 6007, and maker cables and Audioquest interconnect. At some future time, I will buy a streamer.Very neutral-sounding not warm at all( a little sweetness would be nice) I would  not say it is forward as all instruments seem to be at the speaker ( which really do vanish) and behind it. 

I've read on Audiogon many guys saying their listening is within the 80 dB range at their listening position. I played 3 of my CDs to test limits Drum Medicine, Guitar Fingerstyle, and Breath the relaxing strings. My observation 80 + dB is very loud I like it around high 50 dB into low 70 max dB for most music.  So I'm curious what loudness do folks typically listen at? Does the system the music is played over have any bearing on one's ability to sit and listen to 80dB and above for extended periods? ie some systems are laid back, some forward I don't think it would matter as 80 dB is 80 dB, or am I missing something?

 Say I'm listening to Steely Dan's Aba  my system seems compressed at 50dB and below but my System  come to life at my listening position of 8 ft at from about 50 +dB  and creeping into 70ies. My system really wakes up,and hits its stride at 70dB. At 80dB the band is in my room!! imaging, sound stage, inner detail great but it is too loud to listen to a complete album in the 80 dB range it feels like front row at a concert. My amp will be pushed to clipping above 90ish dB ( based on the peak power meters on the amp). I try to max my highest dB level so it won't exceed or just go over the 0 on the peak power meter on the amp, is it ok to push the system further ie -5,-10 on my peak power meter on occasion on some notes but not have the needle sit there? More fundamental what does the 0 and plus and minus numbers mean ie what does -10 represent on the peak power meter?

Some more questions do all speakers( or should I still use the term system) have a sweet spot and a range they play best? Does a system affect that speaker's sweet spot? That is can it lower or raise the range that the speaker plays best?

Are low-powered tube and SS amps limited to playing only on high-efficiency speakers? Since my speakers, optimum power rating is 120 to 200 watts my amp is underpowered at 70 watts, but plays way loud enough but could clip those speakers for lack of power. 

Final questions about my amp it has a tone control for bass, mids, and highs with a range of plus 10 to minus 10 again  what the heck does that mean/represent ? is it the same as an equalizer? 

Speaking of equalizers I am thinking of purchasing a Schitts Loki mini plus putting it between the cd and integrated amp since I have only one source, is this a good idea it seems so? 

And thank you for reading this and for taking the time to give your insights.