Equalization/NR before burning?, Reducing treble/boosting bass before burning. Options

I'm happy both with the ability of iTunes to burn CDs and with the ease of transferring even cassette tape files to the iTunes' library. But in the case of the tapes I'd like to be able to reduce the noise in the treble (not just tape hiss, either) as well as boost bass frequencies.

1. What's a program that allows some equalization and in real-time (so you don't have to keep playing it to see if it worked)?

2. Is the equalization best applied before, during, or after the music has been recorded and saved to hard disk as an AIFF file?

Thanks in advance for any ideas.

Sam

[Synthetic]

Well, I have heard the freeware app called Coaster allows some adjustments to sound but not sure if it is real time. I would recommend maybe using PEAK and get a EQ plug for it or T-racks is another excellent choice for post recording manipulation. T-racks would let you EQ and use limiter and compression to make your cassette recordings sound as best as possible and you can hear the adjustments as you audition the track before applying the FX. Only downside to T-racks is there is no waveform editor so you have to get tracks trimmed in another app.