The touch is lighter, bigger screen, allows you to surf the net, and take your music with you (obviously). Maybe look into the 16GB ipod touch to save some money. The duet remote is a waste if you EVER plan to buy the ipod touch (IMHO).
I must admit I approach the situation differently then you. I have a squeezebox ALREADY, and was thinking about buying the duet remote. CLEARLY the ipod touch is the way to go in this situation, and would provide maximum flexibility. While not the most cost effective setup, it is the way to go, if possible.