Thank you for your responses. Last month I bought a Radeon 6670 and it cannot work with dvi-vga adapter. My adapter didn't fit since 6670's dvi is a DVI-I which had no analog signal.
I don't want to waste my money gambling for something. If the GTS 450 can really works, then I'll go for it.
Oh, I did forget about that. DVI-I is what you want. Two of them, it's the DVI-I that carries an analog signal, as well as a digital signal. It's the DVI-D that is digital only.