I use the Jam; the SonicPort is great if you want a line out for monitors or whatever. If you're just going to use headphones grab the Jam. It's cheap and it works great.
I've had pretty good success with the cheaper iRig. I bought the iRig HD a couple months ago and didn't like it at all. Could not get any sound to come out of the headphone jack when feeding it to my PC/live monitor (but headphones would always work). Back and forth troubleshooting with IK Multimedia and determined it was likely a defective unit. I'll likely get the Apogee Jam next time I'm forking over $$ for a new interface.