Better one would be Radeon R9 280 or 280X
those are around $150-200 more than a 660
Depends on the cards and where you buy them. Most 660's are going for ~$200, you can get a 280 for ~$240 and a 280x for ~$280. You can get a 270x for $180 and it is also faster than a 660. These are based on prices in the US.