The Studio XPS 435MT has a 360-watt power supply (model N248K). It may be rated at 16 Amperes (192 watts) on the +12 V rail, which is weak. This is a standard ATX power supply, in case your buddy wants to upgrade to something beefier like this Corsair CX500
or this SeaSonic S12II 430
The original PSU might be able to power a Radeon HD7850
, which would provide excellent gaming performance. If your buddy isn't going to play the latest 3D games, then the Radeon HD7750
recommended is the best choice.
i7-2600K, H70, P8P67-M Pro, 16 GiB, HD7950, SSD, 3 HD, Blu-ray, X-Fi Ti Pro, Antec P182, S75CF, 3007WFP+2001FP, RK-9000BR, MX518
i5-3570K, GeminII-S524, P8Z77-M Pro, 16 GiB, HD7770, SSD, 2 HD, Blu-ray, InifiniTV4, NSK2480, 55" TV; Asus UX32VD