It'd be helpful to tell us your system so we know what we can and can't fit.
But, as far as watching 60 FPS FHD footage - newer generation Intel CORE CPUs have that out of the box, if you have one. Buying brand new cards, the GT 1030 or RX 550 would both be fine. As far as used, pretty much any decent card within the last 5 years and a fair amount beyond will be plenty.