It's really quite simple, on the left hand side are cards from nvidia, in the middle are radeon, with intel on the right hand side, the closer the card is to the top of the list, the better it is (in terms of performance). For example, the two cards you're refering to here, the gts450 is a tenth level card (it's in the tenth group from the top on the nvidia side) and its' amd equivalent would be HD 4850, HD 5750, HD 6750, HD 7750. Where as the HD6770 is a ninth level card and it's nvidia equivalent would be GTX 260, GTX 275, GTX 280, GTX 460 192-bit, GTX 460 SE, GTX 550 Ti, GTX 560 SE. Once upon a time, both of these cards were at or near the top, but as time goes by and new tech emerges they slowly get moved down. Hope that explains it.