a question about steempower and upvotes

when i started here on steemit a few weeks ago I had 27 steempower delegated to me by the system, and my upvote at full power was giving people $0.02

since starting i have powered up all the steem and sbd that i have accumulated by posting blogs and comments, and by playing poker with the crew at @spl , so now have a grand total of 70 steempower of my own plus the additional 27 delegated... so i would have thought that my vote might now be worth $0.06 , but it has remained unchanged at $0.02 even when voting at full power. oh well...

how much steempower will i need to get before it makes an actual difference to the value of my upvote? i had thought that by buying an additional 300 steem i might raise my vote to $0.2 being about 10x the 27SP that i started with, but am wondering now if it would actually have any effect at all...

if anyone can shed any light on this i would appreciate any answers you may have...