I like loud....it kind of pushes you out of normalcy into the moment of the music.....feeling the stage buckle under you and a warm breeze across your forearms.
Always wear plugs though......but then one tends to turn up which does get a bit silly.
Also, I've noticed that I crank the low end/volume wanting to really feel it....but due to the room (standing waves) right in front of the cab is relatively light on low....one time at one rehersal room I sat on the drummers stool in the corner while someone played by rig and holy cow...those 2 18's were really pummeling. In front of them though, can't feel much.
Massive low end is part of the key to feeling of hugeness...but does depend on where you stand. .
.loud mids are easy to get and the lower ones chew everything up. Its possible my band will be working with a singer live and I really get concerned for balance and sound issues with that - thats something we will have to work hard at.
Heavy overdriven bass just sounds silly quiet - but it can stomp over everything.
With my current drummer he'll often say I'm a bit loud on soundcheck, so I drop back.....then once we are in full flow he's beating the sh*t out of the skins I can't hear myself so well.
Getting the mids right up behind your head helps (again, always wear plugs).
One show I fired up the carvin B1500 and the sound guy quite nicely said "err...the PA can't keep up with that!"

--- 'but its only on 3?!' (owners of that amp who use the drive control will know what I mean!)
A couple of 10/8/6s can provide
plenty of mids providing they are crossed over... its the low end takes the surface area and power.
For sound check, what I do with the drummer is he pedals his
hi-hat while I play...if we can't hear that I'm too loud. Seems to work ok.
We are not playing shows where its all FOH and we have a sensitive sound guy.