Aperture is cheaper and probably a more logical progression from iphoto, however lightroom is more fully featured and adobe are more on the ball at keeping their raw codecs fresh (important if you are buying a new camera) there is a third way, which is photoshop elements.BUT BEFORE YOU SPEND ANY MONEY..
If you are happy to do the heavy lifting as raw and save as jpeg then elements is great value.
Why not install and use the FREE DIGITAL PHOTO PRO
that comes with your Canon camera?!?
It's an excellent piece of software for what it does, which admittedly is limited.
But it will allow you to play with your raw files, make adjustments to exposure, white balance, color, contrast, etc.
With it you will learn to appreciate the amount of post-processing latitude a raw file provides.
DPP also provides that "Canon look" better than the other software and I find that it can also wring the most detail from a properly exposed raw image as well.
LIGHTROOM is an excellent next step, does an awful lot of more creative things than DPP. Can handle hi ISO noise much better and will take you to the next step in image processing.
My workflow includes DPP, Lightroom, Photoshop, DxO, Graphic Converter (Mac only) and occasionally other specialty software. before I had all this I used DPP as my main raw converter and it did a great job. Canon is always updating it and it's been kept free so far so install, update, dive in and have fun learning!