As I said, I really don't know whether those are all the drivers you need. Only Dell can answer that question.
Ask them why they say that you cannot install Windows 7. In the meantime try the virtual route I recommended. It costs nothing, runs real well and is a lot of fun. In appearance and performance you would have a hard time finding a difference to a native installation. Watch the 3d video in the tutorials and this one. It will give you an idea.
My Computer
At a glance
Vista, Windows7, Mint Mate, Zorin, Windows 8from 1.6GHz Duo to i7
Computer Manufacturer/Model Number
HP, Dell, Gateway, Toshiba - 4 laptops and 2 desktops
I bought a Dell XPS8700 in mid October that came with Windows 7 Premium installed. I've since then upgraded it to Win 7 Pro. Works fine here, even after I put in a new Soundblaster Z sound card, and Nvidia 750 Ti video card, as the built-in sound and the Nvidia 720 didn't float my boat.
Update: I have successfully installed Windows 7 on the XPS8700. As for Dell saying it wasn't possible, that was more an issue with a clueless overseas rep.
My Computer
At a glance
Windows 7 Professional x64Intel Core i7-4790 CPU @ 3.60GHz (Haswell)16 GBNVIDIA GeForce GTX 745 4GB DDR 3