Lagging frames

[Stevolution]

Hi

Dug out an old tower PC from the workshop and planning to spec it up a little as my Tekkit machine, as the quite frankly horrific lagging on my Vaio laptop is starting to drive me mad

Frames usually draw, but basically one at a time. The video above (which also has my sfx and speech system in it) doesn't draw the sliding reactor door at all due to the added work of the video recording software.

I have a massive dock crane that stutters it way along the dock laughably.

What is going to increase performance more - good graphics card, better processor?

Are these frames stuttering because the processor cannot work it out quick enough, or because the computer can't draw them quick enough.

I am guessing go for the best graphics card I can +4Gb or more ram. On a limited budget here!