I'm running a 9800GTX+ on an Antec 400W with 25A on the +12v rail. Overclocked to 800/2000/2600 (core/shader/mem), not a single hitch.
18A on the +12v is a little low for just about any modern midrange-highend GPU. You'll definitely need a new PSU for the 9800 series (9800GTX+ equipped PCs generally use about 230W at load, and about 140 at idle - GeForce 9800 GTX+ - Power Consumption), but the 9600GT should work just fine with your current one. Still, the G92 is far less power hungry than its precursors.As I said, it's the cheapest I can get inside the country. And importing is a no-no. My parents simply won't let me import anything of value(in fact, the only thing they let me import at all was two games from Japan, as they came in DVDs. Something this expensive and fragile? My father would never let me import it, even if Newegg shipped to outside North America).
So, I took a look at my PSU(no brand. Damned cheap father). Wattage isn't listed, but amperage per rail was.
Just how good is that? >_>
I don't know much about electricity and it's inner workings, to be honest.