A couple apps come to mind.
One is Amadeus Pro a recorder and editor from Hairersoft which includes a 'repair center' which can remove pops and clicks. It also supports Apple Audio Units, filters that let you do things like filter out subsonics, white noise etc. There is a thirty day trial.
Another is Audio Hijack Pro which I consider a must for Mac audio work. It will allow recording directly to apple lossless format (save disk space) and applying the previously mentioned filters (if used) while recording, thereby saving a post-processing step.
Keep your turntable at least 3 or 4 feet away from your computer to avoid RF pickup. I have been told by audio engineers that external sound cards can provide better results than internals as a result of isolating the analog audio sections from the RF generated by the CPU. Hagerman (hagtech.com) has some good hardware designed for this purpose.
Be careful about removing hiss. Apps like SoundSoap remove hiss aggressively but butcher low level sonics in the process, producing a 'hollowed out' quality. Amadeus' white noise filter is easily adjustable for the best balance between noise reduction and sound quality.
Hope this helps. Good luck with your project. What type of a Mac will you be using BTW?