hi.. i am interested in buying ATI 5670 OR 5660 1gb. my system specs are Pentium(R) Dual-Core CPU E5700 @ 3.00GHz Intel G41 express chipest PSU Watt 450 Hard disk 500gb ram 4gb DDR3 motherboard =asus P5G41T-M LX3
Never seen or heard of the Radeon HD 5660... at least not in the US.
The HD 5670 should be fine. The recently released Radeon HD 7750 consumes a little less power and is a little faster than the HD 5770. The problem is that it is a PCI-e 3.0 card, you have a PCI-e 1.0 slot. Technically, there should be no compatibility issue, but there have been cases where a PCI-e 2.1 card will not work in a PCI-e 1.0 slot.
The real safe bet is to look for a PCI-e 2.0 version of the Radeon HD 5670 since there is also the "newer" PCI-e 2.1 version. A PCI-e 2.1 card not working in a PCI-e 1.0 slot is rare, but it has happened. Does a PCI-e 3.0 card work in an old PCI-e 1.0 slot without any issues? Way too early to tell.