I sold Viking D1s and SEs a long time ago.and almost bought a used D1 but ended up buying a used Pfaff 2058 because of the IDT. If the machine is in good shape you will get many years out of it. You will love sewing with the IDT. Since then I have bought a 2170, Creative 2.0 and a Creative Performance (all used btw) ..... so you might say I'm sold on Pfaffs (lol).
If it is local to you, ask where the machine was last serviced and when. And of course sew on it - try as many features as you can (straight stitch, zig zag, all the buttons, needle up/down if it has one ...). Here is a link to the manual
https://www.pfaff.com/SiteMedia/PFAF...N.pdf?ext=.pdf
You may want to see what accessories and feet came with it and see what the person still has. Don't have a clue what the Creative Designer pad thing is .... almost sounds like some sort of embroidery thing?? You could just call a Pfaff dealer and ask?? Good luck with you decision