Transformer hum with AC fluctuations


I was about to buy an isolation transformer (Tripp Lite) in hopes of cleaning up my inexpensive CDP's sound a bit (Tobias's rec on the cables forum), and now I've run into another AC-related problem.

I live in an old, small rural town in PA, and this time of year power demands start overwhelming our grid: our lights dim for brief moments (a second or so) and then come back to normal all evening long. Coinciding with that--and only at high-usage times on the grid--the transformer of my NAD C325BEE has started making a hum that's audible from across the room. The trannie has always hummed faintly (had to put my ear above the amp to hear), but now it's hard being in the room with it. It doesn't come through the speakers or headphones.

I have two questions: is an isolation transformer likely to hum just as much as my NAD's transformer? and is there a better route to cleaning up my AC (the kicker: within a $200 budget)? I appreciate any other suggestions/solutions. Thanks in advance.
ablang
Thanks for the responses. Shadorne--your APC tip turned me on to them, and I've just ordered an APC H10blk (cheaper line, still true 120V AC conditioning) that fit my price range: $218 shipped from B&H Photo/Video. I'll post again if it's the screaming bargain it seems.
Get a PS Audio Premier Power Plant immediately and this problem will be gone.
Tvad,

Have you used that Channel Islands product? How did you configure it in your system? I've had transformer hum no matter what conditioner I've used.
Post removed 
Well, I said I'd post again if the thing worked--and it does. Even the usual quiet transformer hum is reduced to practically nothing, my TT strobes at the steadiest speed I've seen, and sound has improved subtly but noticeably--better resolution of low-level detail, a slightly tighter bottom end, and improved soundstaging, especially front to back. The EMI/RFI filtration has a good bit to do with all that, I'm guessing. It's the only AC cond I've tried, but I'm pleased--it works, it's cheap, and it's a tank. Thanks for the leads, one and all.