I recently purcashes a late 2015 alienware 17 r3 for 700 on sale. It has an i7,8gb ram ,1tb hdd and 970m. This model is the full hd version not 4k. So i was wondering if i could add components because ive seen other 17 r3 with ssd + hdd and also with sli gpus. Or is my model diffrent?