the higher the frequency, the higher pitched (brighter) the sound is. So if you think the speakers are too bright now, take out that boost at 8kHz, and maybe take down the 4kHz boost to only 1db. Also, bring back up those more midrange frequencies of 500Hz and 1kHz. The "mid-bass" tone you are probably referring too is the 500Hz cut that the EQ has now.
I am kinda surprised the EQ only goes down to 125Hz, my Pioneer Elite (older model) only has a 5band EQ but it goes down to 40Hz. 40Hz is the more rumbly area, 125Hz would probably be considered a bit more of the "boomy" area of sound. Between 125Hz and 1kHz, I would consider "low-mids". 1kHz to 4kHz I consider "high-mids". And above 4kHz I consider to be "highs"