It seems that newer Dell Laptops support SGX out of the box without any update. Just check the BIOS for any SGX option. At least the Dell Precision 17 7000 Series (7710) got that option.

According to different user manuals it seems that you can turn on SGX on the following models.
Source: http://pilot.search.dell.com/sgx

• Dell OptiPlex 3040
• Dell OptiPlex 3040M
• Dell OptiPlex 3240
• Dell OptiPlex 5040
• Dell OptiPlex 7040
• Dell OptiPlex 7040M
• Dell Latitude E5270
• Dell Latitude E5470
• Dell Latitude E5570
• Dell Vostro 24–5450
• Dell Vostro 3653
• Dell Vostro 3650
• Dell Precision 3510
• Dell Precision Tower 3620

If you want to make sure that SGX works on these systems compile and execute the /test-sgx.c

Feel free to discuss you findings regarding newer Dell computers and SGX support here. :)