First of all, thank you for caring! I'm glad that you don't need to be a QUILTBAG person yourself in order to take a stand for what is right. I do, however, have one piece of advice:
Don't postpone your marriage to make yourself a better straight ally.
Now, I don't know you personally, so I don't mean to presume your particular motivation for your actions. But perhaps you happen to share a few common sentiments with others I know who are able to legally marry their partners but are holding off on it because same-sex marriage is still not legal in their region, in which case I appreciate you listening to what I have to say.
First, consider that you're undermining a very important tenant of marriage equality: that "gay marriage has nothing to do with the success of your straight marriage". The most recent example I have is Jay Leno telling Michelle Bachmann that he's been married 31 years, and can't think of a single way that some other person's ability to marry could harm his own marriage. So now I ask you to consider the correlary to that situation: how does your not being straight married help me get gay married? Answer: it doesn't. Unless you consider it to be a form of public attention-raising. In which case...
You can raise awareness no matter what your own personal marital status happens to be. It doesn't take a piece of paper in the pocket to attend pro-marriage rallies, to write letters to congress people, or to donate money to non-profit organizations. Besides, it's just as easy to stand up and say "we're a straight married couple who believe that every gay couple should be entitled to the same rights as us!" as it is to say "we're a straight couple who refuse to marry until all gay partners are able to marry!" Either way, your support of marriage equality is much appreciated, and we hope you keep it up.
This brings me to a third thought. Again, I don't presume to know your personal life, but I have spoken with a few straight couples who feel guilty about their marital status. They feel like they're somehow flaunting their privilege by taking advantage of the superior rights offered to their partnership. They may even feel like gay couples resent their marriage. There are many ways to deal with feelings of guilt, and I can offer one possible solution:
Take all the money you save by being legally married vs cohabiting (or what have you), and donate it to the marriage equality organization of your choice. Any time you would have otherwise had to get a power of attorney, donate that money to charity. Every time you file your taxes jointly, also calculate the rate it would be if you both filed single, and donate the difference. With all that money you save by being on the same health insurance, set up a monthly deposit to your local LGBT center. Bet you never thought of getting married as a fundraiser before! Heck, you could even take a collection for donations at your wedding and at any anniversary celebrations you may hold.
I know there are many reasons people choose to marry or not to marry. I've been married, and now I'm with someone I'm not married to, though we have the legal right if we so choose. Life is complicated that way. But if the only reason you are holding out on marriage is for us QUILTBAG folk, I hope I've given you a bit more to weigh in on your decision.
P.S. If you're one of those people who are using the whole "I don't want to get married till the gays can" card as an excuse to get out of a marriage you wouldn't even want in the first place, you're a turd.