Improving iMovie performance on 1080p by installing a second Solid State HD

iI've been expanding my late 2009 MacBook white unibody 2.6ghz to the maximum.

im in the process of installing a 2tb HD and the RAM is maxed out to 8gb.

unfortunatelly it's I possible to me to view 1080p videos shot with my goPro, 720p its ok.

when I open the 1080p file on VLC It lags big time.

i need to edit some file on iMovie but at 1080p it can be done but the process is not smooth at all.

I was wondering if I was to install a solid state HD instead of my DVD drive and install iMovie on it or even install the whole Yosemite on it do you think I might get better performances Given the fact that the solid state it's much faster than my 5200rpm current HD?

or is just a mafter of graphic card being to old and not strong enough?

as far as I know it is impossible to upgrade it on my macbook

cheers!