The brand of the psu is "power box"? Never heard of that and googling doesn't give much info, which is usually a very bad thing
After some digging around on some webshops in Sofia, best match from what you describe is at
Stealtech, Sapphire R9 280 and r7 370 within 5leva
Dunno how much the budget for the gpu since you didn't mention one, but if you check on that site there is an r9 380 4gb for 420leva which is new gen card. The r7 370 has pretty low performance and can't even play some new games at all. I also found the gigabyte r9 380 2gb at 405lev at
nikemnet and
Sky.