tadej petric :
As I know your wattage is good, but you dont have enough 6-pin connectors. It could run 1 normaly. And theres no need for new windows I only know when you change HDD that you need another one. But with GPU only change you will be 99% fine.
These are the parts Seasonic M12II 620W € 75,00 € 75,00
137769 Corsair Carbide 300R, ATX, Zwart, Window € 86,00 € 86,00
155659 Intel Core i5-3470, 3.20GHz, 6MB, HD2500, S1155 € 189,00 € 189,00
155676 ASRock B75M-GL S1155 B75 2xDDR3 mATX € 59,00 € 59,00
278046 Ballistix Tactical LP 8GB(2x4GB) DDR3 1600MHz CL8 € 59,00 € 59,00
511338 Adapter DVI-A naar VGA / D-Sub (M/F) € 5,00 € 5,00
687069 Gigabyte Radeon HD 7870, 2048MB, OC € 239,00 € 239,00
746512 Seagate Barracuda 7200 500GB 7200rpm 16MB SATA3