I doubt they did anything special.  However the pinouts to the front panel etc are not public or documented.

XPS 8300's mobo is model 0Y2MRG. Also , it is Micro ATX.

It works with

You need a Dell Vostro 460 MIni-Tower Case (GM8J4) w/ 350 Watt Power Supply (9J0VD L350PD-00)

Dell Vostro 460 Front I/O Audio Panel Assembly GY5KV

Dell Vostro 430 460 Mini Tower Case Fan RKC55

This information is not published and is not provided to end users.  

Question: why does the #7 Front panel USB connector (F_USB4) have 11 pins while all other USB connectors have 9 pins?

Answer: F_USB4 is a special internal USB port that derived from standard internal USB port. It has an additional 2 pin to provide 3.3V for the USB Bluetooth module.

Dell Vostro 460 Front I/O Audio Panel Assembly GY5KV

The front plastic panel is KDY5K.

Legend:

1. Front I/O panel connector

2. Front panel USB connector (F_USB1)

3. Front panel USB connector (F_USB3)

4. CMOS battery

5. Password Reset Jumper (PSWD1)

6. Front panel USB connector (F_USB2)

7. Front panel USB connector (F_USB4)

8. S/PDIF connector (SPDIF_OUT2)

9. PCI Express x1 card slot (3)

10. PCI Express x16 card slot (PCI-E1_16)

11. Audio connectors

12. One LAN and Two USB ports

13. VGA connector

14. Two USB ports and One eSATA port

15. HDMI connector

16. S/PDIF connector

17. System Fan Connector

18. Power connector (PWR2)

19. Processor socket

20. Processor fan connector (CPU_FAN1)

21. Memory module connector (DIMM3)

22. Memory module connector (DIMM1)

23. Memory module connector (DIMM4)

24. Memory module connector (DIMM2)

25. Main power connector (PWR1)

26. CMOS Reset Jumper (CLR_CRST)

27. SATA connector (SATA0, SATA1, SATA2, SATA3)

Is the Dell XPS 8300 motherboard compatible with ATX or Mini ATX cases? Yes im sure it will void any warranty, No that does not bother me, but I need a new case that isn't so cramped, and room to perform additional modding.

I installed a standard mATX mainboard in an XPS 7100 case, which is very similar to that of the XPS 8300.