I guess it's a decent card for a budget card, but its not a good gaming card. Secondly, why would you want the 512MB version? Theres no reason you need more then 256MB.
Slightly better, but still, you will see no improvement between 256MB and 512MB models. Unless the 512MB model is the same price or cheaper, don't waste your money on it.
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Actually, the 1650 is a WHOLE lot better than the 1550...