Will My Onkyo 605 Be Enough For the av123 ELT525s?

Listen to them at levels you want. You'll know that way. I wish I had the power break down but it goes like this:

1 watt = 87db
2 watts = 90db
4 watts = 93 db
8 watts= 96 db
16 watts = 99 db

Basically every time you double the amplifier power you gain 3 db. How far you are from the speakers is also important though. The above measurements are from 1 meter and would be less the further you move from the speakers.

Actually this calculator will let you plug in distance from speakers, efficiency, and power.

Most normal people don't listen at loud levels and a regular AVR is plenty. Adding an Amp can add to dynamics and extension, but is the extra cost worth it to you. For most spending more on the speakers would be much more effective at improving the sound.

I just reviewed these below and I used a Denon 2305, plenty of power for moderate volume action flicks and music, plus my room is about 20X30X15 which is pushing it for these speakers...you should be fine, use multiple subs for larger rooms (you can buy an RCA splitter, don't need dual sub outputs)

http://www.hometheaterhifi.com/home-...er-review.html