Power regeneration & regulation if necessary in your home/area, might well be something to continue on with. That said, and I'm not a big fan of Monster anything, you might want to save up some more $$$ prior to making your selection.
If your voltage is stable but your post suggests it is not, maybe a passive cond will help.
My suspiscion is the level of regulator and cond you are using is simply low... and your own recent exp says about as much, given the results from the outlet direct are/were superior to those from the power 'fixin' apparatus on hand.
many of the devices made today do operate thru a range of voltages... from 110 - 125 volts. Mine stays right around 117v. New house & new service, now 5 yr old. Modeerately infested sub urban area.
Brown outs & low voltage situations would concern me too. I'd like to find out just how low they can or do go personally. If under 110 I'd likely opt for a pretty good power regenerator like the Premeir from PSA or some mo' upscale industrial unit from Square D or the like.
I live in an area where thunder storms are fairly regular. Lightening does indeed cause damage even if the stuff isn't energized too, though low voltage gear suffers more readily than do well built amps, as do abrupt off & on power cycling or interruptions from things like tree limbs touching the power lines..
For me these items are a pretty big concern so I use PSA & RSA routinely. If I could afford more I'd opt for a better RSA unit than my present Haley as I have no low voltage issues and don't require regulation..
Otherwise, if things sound great out of the socket... play your stuff that way. Mo betta power conds will genarelly provide you mo betta results.
Other's here might be able to point you towards one for $600 which can help. I'd say again, a larger investment there likely will be required for your particular situation.
Good luck.