I would sugguest getting the editor that suites your workstyle and has an interface that is easy for you to understand. Looks are important, but even more so is ease of use and power of features. Don't just buy what "feels" right, buy what makes the most sense to you... But why go guessing when you can download the demos and figure out which one you like most????
I think peak is the best out of the native to mac options. However, that's just my personal preference. I tried out wave editor, and didn't like it's interface. I find it slower, cluttered and less intuitive to use than peak. That being said, I didn't spend a lot of time getting to know it.
IF you go soundforge, run it via crossover:
http://www.codeweavers.com/products/cxmac/
this way, you don't need to dual boot. It just runs in OS X
As far as Audiofinder goes, I *LOVE* this program, but it's not really a full fledged audio editor. I think you'd find that you'll be limited trying to do any intermediate to advanced audio editing in it. It's really designed to be a file organizer, and for that purpose, it's great. But as far as audio editing goes, it's not really a good option.
I really think the best thing to do in your case is to demo these and find the one you like best. Buy it, and learn it well. The way I see it, an audio editor should be something that you can use and flow with quickly so that any editing you're doing doesn't take a lot of time or energy away form being creative.
try these out to start:
http://www.bias-inc.com/downloads/freeTrials/ http://audacity.sourceforge.net/ http://audiofile-engineering.com/wave_editor.php
remember that though it's not the best, there's a built in audio editor in Logic too!
you could always spend the money on other cool gear and get to know logic's editor well. That being said, I'm pretty sure that the options we talked about here are more in depth and potentially easier to use than logic's audio editor......