Fermi is the architecture used in the gtx 4xx, 5xx and the early gtx 6xx models that are OEM only as well as some workstation cards. Kepler is the architecture used in the gtx 640, 670, 680, 690, 660m, 680m, and soon to come 650 and 660ti. Quadro is a workstation card for professional work, as well as Tesla I think.
gaming wise, you essentially aim for Gtx ### model gpus where the 1st number represents family and generation, and the second represents how high in the family it is for that generation. last number is usually 0 and thats just to make the number look good.(onyl special occasions is when its #85)