To Filter or Not To Filter . . .

I don't know if I have a problem that needs fixing. I live in Northern California and currently do not implement any sort of power filtration, conditioning, or surge protection devices. In short of trial and error, how do I know if I need these or not? I am currently using rhodium A/C receptacles with VH audio flavor 4 power cables with rhodium connectors. Thanks!
Are you using dedicated lines? Should be your first priority....I wouldn't buy any filtration or Conditioning unless going the Dedicated lines first........
What if you live in an apartment that you are renting? I also live in Northern California (San Jose) and, like the original poster, have upgraded receptacles and decent power cords.

I bought an Audio Magic Stealth XXX several years ago, and it made a vast improvement with regards to the background silence of my system. The results were more what was not noticed until it was gone(background grunge), than something added. It allowed me to better appreciate the detail/microdynamics/ambience retrieval/etc of my system than before. I recently replaced 120ft of 12-2 Romex running to my room, with two runs of 10-2 Romex(equiv. to 4AWG), and what a difference in dynamics/speed! If you have no dedicated power to the room, either will still present you with an improvement/both will be a revelation.
I do own my house, and will look into making dedicated lines to the room. That sounds like good advice, and a good place to start. I do hear noise in my speakers when the amp is on and no music is playing -would this be considered background noise from A/C, or just normal amp noise?
First, CYA. Get a Brick Wall surge supressor to protect your equipment from lightening strikes. Or, you can have an electrician wire a whole house surge supressor in on your main panel for under $100. Now you can sleep at night knowing the system will be there to listen to. Next, borrow or trial/demo a few line conditioners to evaluate results. I'm confident you'll here positive improvements. Lastly, when the time is right, run a sub-panel to support your A/V system and Audio system. Run dedicated lines and keep the analog on a different leg than the digital. Suggest Porter Port outlets. After the dedicated lines are in, you'll be amazed at the improvements. And the room lights wont dim when you crank it up........... Good Luck.
I do hear noise in my speakers when the amp is on and no music is playing -would this be considered background noise from A/C, or just normal amp noise?

It could be a lot of things, and it's hard to say without more info on your system, and without doing some experiments. My guess, though, is that if what you are hearing is a low level hiss, that is always present at the same level, it is not related to noise on the ac line.

Good power amps are usually pretty quiet, but if you have highly efficient speakers (e.g., 95 db/w/m) that increases the likelihood that the power amp is the source of the noise. If they are inefficient (e.g. 85 db/w/m) the power amp is unlikely to be the source of the noise. Do you still hear the noise with the inputs to the power amp disconnected? Obviously, do not disconnect them while the system is turned on.

Is the noise independent of which source component you have selected, and is it independent of the volume setting on the preamp? Turn off (and preferably disconnect) as much as possible to try to localize it.

Another significant possibility is pickup in interconnect cables, contributed to by inadequate shielding in the cables or by close proximity to power cords or other noise sources.

Also, if any of your components have 2-prong unpolarized power plugs, try reversing the polarity with which they are plugged in.

-- Al
Filter. The question should be which not if?

Dedicated mains if you can. If you are really going for it separate source and amps or digital and analogue.
Thank you for all of the advice thus far. While I'm installing a new panel, surge protection, and re-wiring my room, are there any filtration devices that can be installed in wall or at the panel, something to take the place of a conventional stand alone unit that plugs into the wall?
PS Audio has a new device similar to their Ultimate Outlet that installs flush in the wall. So it looks like a large wall outlet. But eliminates another box on the floor and an AC cord. There are large isolation transformers that can be installed near the panel. Low WAF but great for that Frankenstein look. And of course, several companies offer high quality in wall AC wire.