Hi RHarv and any interested others,

Firstly, thanks for your generous help with my issues so far. Much, much appreciated.

I struggled on for some time trying to work out why my set up wouldn't truly pan as explained above. I put into place all the suggestions RHarv offered, but no go.
Now, I have a Jam Vox as well, which is basically a USB powered external sound card for gtr practice, but with which it is possible to record to a PC. I found I could pan track content within PT17 as desired using the Jam Vox, so concluded the problem was with the Delta PCI card.
Although I focused closely on the Delta and did everything I could over about 2 weeks to get it to work fully, I just could not find the causitive issue. So I went out and got another interface, an M-Audio M- Track Quad ($349 AUD). Also USB (2.0) connected, but additionally using 6V 3A power. It is taking a bit of time to come to grips with this unit but the signs are good that it will work well with the new PC. And yes, I can pan track content now. So I said to myself "what the heck" and indulged in a nice pair of Beyerdynamic DT 880 Pro Studio headphones as well.
So all up, a mere $2K AUD to get a happening combination but what price sanity?
Again my thanks for your willingness to help a mug 10,000 km way. I hope I can post the results here before too long.
Cheers,
John