PC upgrade

I am looking to upgrade my current home PC.
MY Current PC is 8 years OLD ( 2.4Ghz p4) and I presume only re-usable components are graphics card ( geforce 210 ) and 1TB HDD ( not 3 Gbps though ) .

My primary OS will be windows 7 and Ubuntu for some development tasks.
My use case include following .

1. Daily net browsing . ( tend to keep number of browser tabs open )
2. Connect to office VPN and work on remote desktop.
3. Occasional kernel / application compilations
4. torrent downloading seeding ( may run overnight )
5. FullHD youtube video play. ( main reason for upgrade )
6. Full HD video Play. 7. I may not play any kind of game ( max I play is angry birds   )

After searching a bit I thought of selecting following components.

1. Motherboard gigabyte 78LMTUSB3

2. CPU FX4100

3. a Cheap 4GB dual channel RAM with low CAS

I am looking for a VFM combination . Kindly let know your thoughts . I am open to chose an intel combination if it is worth and VFM. I am looking for a combination which can run 6-8 years without any major upgrades ( I am not a gadget freak   ) .

Thanks An