Sounds like you need to set up your toneport as your sound card, so that you can monitor your recorded signal. You need to do that in the Audio Preferences tab of your computer. Essentially you disable the on-board soundcard in your computer, and your Toneport becomes your soundcard. If you set at as the "ASIO soundcard" your computer should recognise the Toneport as being plugged in (using the USB cable that came with it). For this to work, however, you'll need to plug your phones and speakers into the appropriate outputs on the Toneport and not the computer. The Toneport soundcard capabilities will be in advance of those of the onboard soundcard, especially as regards being able to monitor without any delay (useful when adding additional tracks to already-recorded tracks and getting them in-synch).

With the appropriate cables and connectors you can plug your computer speakers into the Toneport (from the "Analog Out" L & R 1/4" sockets on the back, or preferably buy yourself a nice pair of powered monitors (but plug in your monitors to the same power outlet as your computer in order to minimise the creation of a ground loop which will give you mains hum).

When you have this set-up you should be able to check that the Toneport is functioning correctly as your soundcard by trying to play from another source on your computer (such as iPlayer or Windows Media Player) - you should hear the tracks being played through the speakers and the headphones plugged in to the Toneport.

If you've already done all this, and you're hearing your iTunes ok but not your Logic, then it's probable that you need to adjust something on the output side of Logic (though I haven't used that DAW, so you'll need to see what you can do in that respect).

Good luck,

Clive