I would upgrade the PSU if you want to go with the 6670,
Now new AMD gpus are coming, and they look promising, maybe wait for the new gen,Radeon HD 7770 Pictures, Plus 3DMark Benchmarks
Nothing is secret in GPU land as it seems, the leaks keep coming. ChipHell has leaked more pictures with some benchmarks to go with them. The test setup consisted of an Ivy Bridge ES CPU – Core i5-3550K at 3.3Ghz and Z77 chipset-based motherboard. The driver used was the AMD Catalyst 8.940 RC2, giving the following 3DMark benchmark results:
HD7770 (Stock @ 1Ghz): 18143 3D Marks (SM2.0: 6785/HDR: 8086/CPU: 6390)
3DMark 11 (Performance Preset):
HD7770 (Stock @ 1Ghz): P3421 (3138 Graphics Score)
3DMark 11 (Extreme Preset):
HD7770 (Stock @ 1Ghz): X1077 (965 Graphics Score)
It was already known that the product has four memory chips on the upper side, but this shows that there are four extra chips on the underside.
In other words, the adapter possesses 2 GB of GDDR5 VRAM, clocked at 1.125 GHz, instead of just 1 GB. the memory interface is of 128 bits and the GPU clock speed hovers at 1 GHz (the first GPU to break the 1 GHz barrier without factory or home overclocking). Other specifications include 896 stream processors (SPs), support for DirectX 11.1 and compliance with the PCI Express 3.0 specification.
Finally, the thermal design power is rated at between 90W and 100W (a single 6-pin PCI Express connector supplies the energy). We expect pricing to be 150 USD / 119 EUR.
We will probably see other cards in the months to come, and probably Asus, Gigabyte, Powercolor and Sapphire might continue their passive heatsinks designs.