Not sure here. A 5770 is going to be bottlenecked by the 2.8GHz P4. The low CPU bound res will also be a problem. Thankfully you only need 60FPS so I think he'll be ok, assuming the P4 is good enough to provide 60FPS. With a 630i, I would grab a C2D pretty quick. You should be able to run any of the duo, though your limited to the 65nm quads.
Performance wise GTX 260 216SP is better,but 5770 runs cooler,quieter,and supports newer techs like DX11,eyefinity,and for your resolution,like i said a 5770 is more than enough.
But like others said,i would recommend upgrading the CPU too
It should work, but I've seen some threads on other places wherein they're having problems. It'd be best to check other forums if they have been able make a 5770 work with a 630i.
Worst case - would be incompatible and there'd be no BIOS update available
Semi-worst case - BIOS update would be available but there would be some problems (i.e. long time to boot)
Good case - BIOS update is available and there are no problems
Best case - Would work without a BIOS update
Here is an old but good review http://www.tomshardware.com/reviews/crossfire-meets-pci...
"For now, the move from PCI Express 1.0a to 2.0 does not result in a performance increase with the current crop of graphics cards. Despite the fact that it doesn't feature the PCIe 2.0 interface, ATI's Radeon HD2900 XT gains two percent more performance, as do the HD3850 and HD3870, as well as Nvidia's Geforce 8800 GT. Such a small improvement could have many causes completely unrelated to the new interface, such as the newer chipset, slightly higher system memory frequency, or simply margin of error.
Whether or not upgrading to a P35 or X38 based motherboard is a worthwhile investment for a single-card system is a matter of personal preference. If you're building a new system from the ground up, we would recommend choosing an X38 board with dual x16 connections for a Crossfire setup. Upgrading a Crossfire system from an Intel 975X or P35 chipset to an X38 will only pay off if you play at resolutions of 1920x1200 or higher."