Are upgraded power cables really worth the money?

Imperative upgrade imho. I recall the day a few years ago when I first introduced a decent power-bar (appr. $ 150) and 2 after-market cords (each appr. $ 100) in my system. The dealer had lent the gear to me over the weekend and I never returned it; it was like drinking a nice cool beer from an appropriate glass when you're really thirsty instead of the bottle-neck or a can.
Try and find someone who will lend you cords for auditioning before you open your wallet. I think you'll find it rewarding if you went for something in the price range I cited. VooDoo Cable's entry level could be one starting point. One of many, I'm sure, but I have found Bruce's recommendations very precise and valuable, surely an advantage as you may have to lend special attention to the sub.
Good luck.

In my system, the power cords made the most significant difference. I started at the CDP with my best cord and added one at a time and listening to the same song over and over til I got the speaker cables added. I tested several cords and cables and the Shunyata got the place in my system. You could spend quited a bit on Shunyata power cords and they are worth it IMO. A budget plan for Shunyata would be an old Cobra Red label or python for the cdp, and a Diamond back for the integrated. this would be under $700 used here. You could go with python helix if you have more budget and put them everywhere like I did. I started with the budget cords I mentioned and eventually sold and replaced with new helix. you could get more lower on the budget. What would your budget be on PC's.

beerdraft

Yes, upgraded power cables are a good investment. I admit I'm spending a bit more on them these days then when I first made a purchase. You can spend from $10- $12 on a Volex or thousands of dollars on the exotic cables. I refuse to spend that kind of money. I started out with lower priced cables from Shunyata, even the dirt cheap Volex, but eventually graduated up the food chain a bit. In my opinion, of all the cables you will purchase, the power cord can reap the most benefit and also do the most harm. So, auditioning in your system carefully before purchase is critical. As suggested, buy a cord you can audition for at least 30 days in your system. If you don't like what it does when connected to your gear, then send it back for a refund. There are companies and dealers that provide auditions. I would look to dealers that provide demo power cords that can be auditioned. Also, the Cable Company will lend you cables for a small fee. DCCA and VH Audio sell quality power cords, have great customer service and also have audition periods on all their cables. Don't make the mistake of auditioning more than one new power cable at a time. More than one new cable in your system at a time makes evaluation of each cord practically impossible. I also belive in power cable break-in. (some don't) It's important that you allow a new power cable break-in time and time to settle in once you connect it to your gear. As you know, once any cable is connected, it should be left untouched and given time to settle in. The sonics of your system will change during these periods. After break-in is complete and the cable has had time to settle in, then make your final judgement. It takes time and patience (which I never had a lot of). Good luck with power cords.

I use PS Audio Statement Extremes on my cd palyer, pre-amp amd amp. There was a significant improvement to the cd palyer in the form of a much blacker backgound. I heard no significant improvment over the stock power cord with my amp or pre-amp. And I have not experimented with any other power cords.

Chuck

Yes --unfortunately :)--can be a very dramatic improvement!