No such thing as a low profile GTX960.
Also Requires 300W just for the video card.
(Slim models have 270W or LESS for ALL OF THE Voltages.)
You cant put a 650W or larger power supply in that unit.
Radeon HD6450 would also work with Secure Boot OFF
CSM ON Legacy Option Roms ON. Has to be Low profile 1 Slot wide and cannot have a fan sticking up.
Thats why Geforce 210 or 610 LOW PROFILE cards are the only ones that PHYSICALLY Fit the case and don't use too much power.
EVGA GeForce GT 610 02G-P3-2619-KR
GT730 OEM LOW PROFILE DELL Card.
You cant use a full size card. Dell modified the amount of ram and clock and other items to get to a specific power profile.
GTX 9XX Anything is NEVER EVER going to work or physically fit.