A dream card for high end gamers,this 800 stream processors equipped ,55nm baby runs all games decently @high on the most used 1680x1050 and at full HD 1920x1080p easily,the most attractive part about this card is its power consumption,runs fine with the power supplied by the pcie slot(75 watt) on the mother board and 2 PCIe 6pin connectors

Have a look at its specifications .

Radeon 4870 1024 GDDR5
# of Stream Processors 800
Core Clock 750MHz
Memory Interface 256-bit
Memory Clock 3600MHz
Memory Type GDDR3
Memory Bandwidth 115.2GB/sec
Texture filtrate 32 Gigatexels/sec

Dont get confused seeing the 256 bit bus interface and underestimate its power , the rv770 acrchitecture is a brilliant innovation and ati was known to be working on this rv7XX architecture from 2005 and result is known to us.
It beats the 256 bit ati 4850. Due to 55nm die and 256 bit bus width its power consumption has been minimized .

The 4870 gives the geforce 9800gx2 (its nvidia competetor ) a run when AA turned on.
And u can say this card is somewhere near to the geforce GTX260 Core 216, as it is found to beat it in certain games like crysis and call of duty 4 (source guru 3d).
Though the Core 216 is a bit better in performance but still if a person is opting to shell out around 13000INR or 200$ he/she definitely can afford for 2.5k more for the psu.So id rather sugest to go for the 4870 than the GTX 260 Core 216 + branded power supply for 5% or no performance difference.

gpu-z

Its performance
setup core 2 duo E6550
ati radeon 4870
4 gb 667 mhz ram
windows vista x64 service pack 1
people having better processor may get better performance .