Sounds like you've gotten some pretty good advice so far, but I thought I'd chime in with my $.02, since I have had a slightly different experience than some of the above posters. I currently own the Hydra, the P300, just purchased the EP2000, once had a P600, and have demoed the Equitech (older version). I would offer you the typical audiophile caveat - none of these power conidtioners is the universal fix-all, working the best with all components (which is why demoing is so strongly recommended).
Honestly, the least effective product in my system was the Equi-tech. It reduced background noise somewhat, but muted dynamics with both amplifiers and my Thor TA-2000. It was somewhat better than an old Monster PC I use for my home theater system, but that's about all I can say for it.
The Hydra is an excellent piece of gear, which I currently use on my Air Tight ATM-2's. However, I found the Hydra to fall short of the P300 with digital gear, and particlarly with turntable power supplies.
The Power Plants are very component dependent - back when I had CJ 8XS's, the P600 sucked the life right out of them - which is what motivated me to buy the Hydra. On the ATM-2's, both the P300 and Hydra both offer an improvement over straight into the wall, although I slightly prefer the Hydra's presentation - a little warmer tonally, more relaxed presentation, better dynamics in the ff-ffff range. On an intellectual level, I hate the Hydra (I was once a EE), because I'm not comfortable with the technological explanations offered as to why it works, but I can't deny the improvement in sound it offers.
However, I am really jazzed about the new EP2000 I just picked up to try with my system - it offers many of the benefits of the P300 (maybe not quite the same reduction in noise floor), without the limited dynamics on amplifiers. Right now I am having a shoot out between the Hydra and the EP2000 for my amps/preamp, but haven't come to a definitive conclusion yet. I am looking at picking up some used Shunyata KC power cords (currently using all Electraglide Fat people), and trying that with the EP2000 to see if I can get the benefits of both (the Shunyata power cords supposedly work on the same priciple as the Hydra - use of FeSi).
In sum, if you want one conditioner for all of your components, my recommendation is to go with the Hydra or the EP2000 - or if you want some of the benefits of both, try the EP2000 with some Shunyata power cords, and let me know how it works out.