[SOLVED] Should I upgrade GPU or CPU to have smooth 1080p video playback on YouTube?

[Edember]

I have a emachines EL1352G-41w computer here with AMD Athlon II X2 220, 8gb ram and a GPU of Geforce 6150SE which is pretty sucky. The performance is pretty fast with SSD installed but 1080p HD video playback kinda stutters on youtube, and some ui scrolling on html 5 stutters a bit. Which should i upgrade so video playback wont lag? cpu or gpu? I dont want to spend a lot on this, (bought this one for $15) plus if i upgrade the CPU and GPU at the same time i might need a new power supply.

 

[Alabalcho]

What is the "maximum" CPU your board can handle? Does this CPU needs updated BIOS?
You will probably need new PSU anyway if you upgrade the GPU.