Is there a way to make the volume envelope in Vegas go higher than +6dB? I recorded a wedding in a big church with the mics on my Sony D50 @ 24bit/96KHz and there are some parts of peoples' speech that I want to raise a bit more.

No. But you can raise the entire track +12 in addition to the +6 from the volume envelope. You can also "normalize" the audio which will take the loudest point to a certain level. Plus the compressor can also be used to increase volume.

I already edited the wave in Adobe Audition. I just wanted to raise a couple parts of speech a bit more than the 6dB Vegas allows.

Perhaps you can split the track where you need to raise it, render it to wave and rerun the envelope or use the volume FX or AMP MOD FX to get it where you need it on just that one section. Drop it back in and you should be good to go.

I played around with the envelope process in Audition and got those parts up a bit more. The Vegas volume envelope is just a lot simpler to use. I can raise it a bit more in Vegas and I think it will be about where I want.