RS-MMC Dual Voltage Pros?!
 

What do you think? Is it better to get a dv-card? Is the 770 supporting 1,8V? Thx!

You won;t get any benefit from a DV card in th N770, as it would only use the 3V setting. However if you have another use for DV card, ie in a phone, then it would be worth it.

....or you can save your cash and getting a bigger card :)