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Only short cards 8.5 inches or less fit into the case and if its a 660S then only short LOW PROFILE cards fit.
Agreed, The Inspiron 660 300w power supply can support the GeForce GT730 as well as the following Dell OEM video cards =
CJF72 Nvidia GeForce 640GT OHGA3 (Windows 8)
YG17P Nvidia GeForce 640GT OHGA3
98KC7 Nvidia GeForce GT620 M117N
51NCR AMD Radeon HD7570 M209A (Windows 8)
0NTVR AMD Radeon HD7570 M209A