The Gigabyte GV-N770OC-2GD and GV-N780OC-3GD are good video cards. Their performance is in line with other GeForce GTX 770 and 780 cards, and the overclocking potential is fine. A strong side of these cards is how silent they are when idle.
Any major computer upgrade generally requires a full software reinstall too. No so if you heed the advice in the guide to Upgrading a Motherboard without Reinstalling. PCSTATS Tips