Music is the soul of a party. Ask Van Wilder, he'll tell ya. If you don't have it your party loses momentum and feels like its full of awkward pauses. Now I'm not saying blow your budget on the highest form of entertainment money can buy. Its important... but not THAT important.
At our wedding celebration we did have a DJ for the reception, but we had a boyfriend of a bridesmaid play DJ at the ceremony. It was a short ceremony so it seemed silly to hire someone for it. I made a CD (actually I emailed him the songs and he made it for me, very very last minute. Thanks Trav!) of the four songs I wanted to play during the ceremony and all he had to do was press play on the CD player. $AVINGS TIP: Using a CD of your songs, as opposed to hiring a pricey string quartet guarantees you'll not only know the songs that are being played but you get to say what is played. Be sure that your venue has access to a CD player/sound system before going this route. Luckily ours did.