Hi chino917,
5 beep error code indicates an issue with RTC power and indicates an issue with CMOS battery. You may try reseating CMOS battery. You may refer to Owner's Manual Here. The location of CMOS battery is as shown below :
The video cards mentioned by you should function properly, however, Dell has tested XPS 8700 only with following video cards :
- nVidia GeForce GTX 660 GTX 645 GTX 650Ti GTX 660
- AMD Radeon HD 7570 HD8870
Hope this helps.