Will a voltage regulator improve sound?

Go with TrippLite. It's a great product that will NOT color or alter the sound but WILL protect your equipment.
The purpose of any surge-protector and voltage regulator for audio applications is not to alter any equipment performance.

If you live in a home built in the 50's or older, the problem is probably due to wiring.

I used to live in San Rafael in a home built in the 50's. It had a 100 amp service panel (as most older homes do) and there were only 4 circuits for the entire house.

To make a long story short, every time the dishwasher and/or microwave and/or washing machine and/or refrig motor were running all the lights in the house would start to flicker for the duration.

I know CA has it's electrical issues for everybody, but I'll bet it's the overloading of circuits that you are experiencing.

If you do not have dedicated lines (or at least one) from your service panel to your equipment, if you had an electrician install one or more, it may help. And while he's there, (assuming your home is an older home) you could inquire about moving appliances around on the service panel, dedicating the lighting to their own circuits, etc. which may resolve some or most of your problems.

-IMO

Most surge protectors will give a blacker background, but at the expense of dynamic range.
This is especially true of the cheaper ones(under $1k)

Make sure you can return it for a refund if it doesn't perform to your liking, whatever you decide to buy.

John C.