You should do ok with the 4850, it runs decent settings.
Won't get the very latest dx11 candy, but other than you should be fine.
All the other components are fine, except for the PSU.
For the cheapest reasonable get Antec 380D $52.99
OCZ ModXstream Pro 600W $69.99 before $25 MIR is 'ok' as well.
Antec HGC series and Corsair Gamer series are ok too.