MacTheScope is the industry standard RTA for Mac. The program is quite awesome graphically and provides all the functions you are like to need. They have an OSX version out for at least a year-- so the bugs out to be getting worked out by now. The full version is $449.
You can download a demo version free. It does preclude saving files and printing results, of course, and other limitations until you pay to get the activation code. From their web site
Mac the Scopeā¢ 4X 4.22 (All In One Installer)
* Installer includes Mac the Scope 4.22 and Waavebox 1.72, plus documentation and support files.
* Installs the time-restricted demonstration version. Unrestricted software is installed with a Version 4.1 or later activation code.
* Complete pricing and configuration information can be found at http://order.kagi.com/?UUJ.
System Requirements
* Mac OS X 10.2 or later. OS X 10.3 Panther preferred.
* 500 MHz or faster CPU. Sample rates higher than 48 kHz may require faster CPU.
* 1024 x 768 or better screen resolution.