Both the 1gb Radeon HD 7750 and 1gb HD 7770 are PCI-Express 3.0 cards. What amount (if any) is video game performance difference is there between a Radeon HD 7750 and a Radeon HD7770 in an older system with only a PCI-Express 1.0 x16 slot (motherboard is Asus P5LP-LE w/ parallel printer port also know as HP Emery-UL8E with chipset Intel 945P Express, cpu Intel Pentium D 920 @ 2.8ghz) running MS-Win7 (I also duel boot to LINUX, but do little gaming in that space)? Since both cards will be step down to PCI-Express 1.0 x16 interface throughput, is there any performance diff between them? At writing, there is a $25 cost diff between the two video cards, but the HD 7750 box claims it will work with my exiting 300 watt power supply. If I go with HD 7770 I would also need to install new 500 watt power supply, which with how the HP Media Center PC is wired, is an intrusive job. I see ATX 500 watt 80 plus silver power supplies going for $60, so if I don't break anything during install, going with HD 7770 is going to cost me $85 more. Will I see $85 worth of greater performance with the HD 7770 in a PCI-Express 1.0 x16 slot over the HD-7750?
From research I have done, it appears to me that both cards will work in the PCI-Express-1 x16 slot in my old system. I not sure what you mean by "best deal"? Question is; does the HD 7770 perform better than the HD 7750 when both are downgraded by being in a PCI-Express-1 x16 slot? If yes, how much better? $85 worth better?
I should have mentioned the games I play, sorry. They are; flight simm, skyrim, and heroup (later is off the internet).