goto "Richie Street" (near Mount Road), but take someone who's experienced in bargaining & with these items (PS2).
Enter the "Richie Street" from near the "Bata Showroom", & ask someone about "MOOSA" shop, its on right hand side just 2 buildings away from there. the shop is in basement.
You can also try other shops that are in the same complex.
at first those guys will start with Rs.8000/-, you just tell them that you/ur friend have already bought a ps2 for Rs.6500 (your quotation) from their shop.
XBoX360 is also availabe in "Richie Street" but you've search in other shops(in same complex).