You do realise that everyone is going to hate you for going from an I9300 to a loaded m1730. Well, everyone except those who have m1730s. As for those pushing... Keep pushing, from what I've noticed, Dell reps are often number-based... so to them, 8700 > 7950. However the enlightened know that the first # = generation, the SECOND # usually correlates to the performance levels. If you're being screwed around, show them hard numbers... nVidia used to have them, but they seem to be MIA the last time I checked.
It doesn't necessarily hurt to find a big database such as GPUreview.com (a compendium of video cards and everything) and show them the comparisons of the card you received compared to what you have. If they see hard data, it becomes much harder for them to attempt to disprove you.