If voting could make a difference

OK, I voted yesterday... did it make a difference?  Or does gerrymandering make my vote irrelevant?

I live in a heavily Republican district in New Jersey.  It's gerrymandered that way, and a Democrat has virtually no chance of winning.  I voted a straight Dem ticket, but for both the Assembly and State Senate races the margin was approximately 65/35 for the Republican incumbents.  

We did better at the county level, with Dems being reelected to County Freeholder.  Also statewide, the Dems did take control of the State Senate and  expanded their margin in the Assembly by 6 seats so there is good news.  This pickup, despite an unpopular Democratic governor has to be a good sign.  

Turnout was obviously light for an off year election with the State Senate and Assembly races heading the ticket.  Although I couldn't find any figures yet, in 2001 turnout was 31%.  Given that the number of truly competitive races is small, I wonder if people aren't making a rational decision to stay home on election day.  

The counterargument is that the fewer people who show up, the more my vote counts, but it seems like the system is rigged.  I think the answer is that it will take more than just voting to change things (although that's an obvious start).  It's time to get more involved, not less.  Donating to local candidates will give more bang for the buck than giving to the national candidates (although I'm doing that too).  Time to give of my time also.