I have used both Journeys Out Of The Body and Gateways CD's and what I've had most success with is the Gateways. I just never spend as much time with Journeys as with gateways, so thats why. Never the less, Journeys have yielded some results to and its good you ask about listening to them in a sitting position because I have some feedback on that.
Most of the time when I have laid down in bed and listened to Journeys or Gateways I have fallen asleep. I know that its the worst possible place to be when meditating or trying to induce trance states since we are programmed to sleep in our bed. But I also sit up meditating in my bed, and this works perfectly good for me. When I use the CD's sitting I get good results, and when I use them when in a half sitting/half lying (with head support) I tend to get the best results. I can imagine the Journeys CD's to suit you since you already meditate and are used to do so without guidance (the Gateways is guided, whilst the Journeys are mostly not (just sound)).
I would also recommend starting from track A on the CD and going forward. The times I've started with D I've fallen asleep pretty quickly as I'm not used to going so fast down to Theta/Delta.
I feel that they really do help. I've gotten deep in to trance states much more easy and fast than when only meditating. I understand its individual in how you respond to the signals but no other binaurals or sound technology have done anything for me. For me Hemi-Sync is the real deal.

Good luck!
//Linus