Use the search function or just browse the video card section. There's already tons of threads on this.
i'll just answer the question pci e 2.0 doubles the bandwidth from pci e 1.0 allowing more info to flow through increasing performance, and yeah you can use a pci e 2.0 card in a pci 1.0 slot. you will notice a performance increade though if you put the 2.0 card in a motherboard with a pci e 2.0 slot
you will notice a performance increade though if you put the 2.0 card in a motherboard with a pci e 2.0 slot