if your budget have at least $350 for motherboard and CPU then
i5 2500k ($220) plus asrock z68 + extrene gen 3 $125 would be the way to go.
it got hd3000 which is a stronger igpu, powerful CPU and ability to overclock later on.
at lower budget around $270 then i5 2400 ($190), i5 2300 ($170) plus ASRock H67M ($80) Hd2000 igpu are weaker but still able to handle office workload and it got hardware acceleration for video decoding.http://www.newegg.com/Product/Product.aspx?Item=N82E16813157233
even lower at $200 then you got duo core i3 2120($130) and i3 2100($125) plus MSI H61M-P21($60) missing things like USB3.0 and SATA3.http://www.newegg.com/Product/Product.aspx?Item=N82E16813130603