Is it better to have 2 x 512MB Gainward BLISS 8500GT or just 1 Power Color 1GB HD3650.
Depends what you are trying to do... Well actually SLI is pretty stupid on lowend cards. The performance of both is usually lest than a single model higher card. The HD3650 would be the better of the choices.
What are you planning to do with these cards, that is the big question.