Don't know if arkaos uses GPU acceleration, but most likely the problem will be a wrong codec.
For resolume you can use DXV, a gpu accelerated codec that speeds things a lot up! If you don't want to use this, you can use photoJPEG (most of my "normal" content is photojpeg, only the best clips are dxv because it takes a lot of hard drive space).
A vj program shouldn't have problems with a quadcore. My previous computer had a Core i5 (1st generation) dualcore and hd5650 and it could handle 3x 720p.
A SSD will have faster clip loading, but honestly I don't have any problems now with my macbook 5400rpm drive, still acceptable fps.