Hello Nick212,
You can get the NVidia, GeForce GT620, 1DVI-I, 1HDMI, Low Profile, M117N (Win 8 Support) for the Inspiron 660s through Dell Spare Parts (US Customers only).
The following is the part numbers for NVidia, GeForce GT620: RGM3T.
You may contact Dell Spare Parts and order the above mentioned graphics card. Contact number for Dell Spare Parts sales team # 1-800-357-3355 (US Customers only).
Please write back for further questions.