Final Fantasy XIV will be out on PC WAY before the PS3 version. But do you need to upgrade your PC just to play it? Not necessarily as the system requirements are fairly light:
Windows XP/Vista/7,
Intel Core 2 Duo 2GHz or AMD Athlon X2 2GHz,
2GB of RAM,
15GB HDD space,
NVIDIA GeForce 9600 512MB or
ATI Radeon HD 2900 512MB and
DirectX 9.