I'm lookiing to upgrade from Creative Audigy and buy the new Layla 3G card.
Also want to get into 5.1 mixing in Vegas. Will the Layla 3G allow me to connect with the M-Audio LX4 5.1 speaker set?
The Layla has 8 independent 1/4" balanced line outs that can be configured as either four stereo pairs, a 5.1 set, or a 7.1 set using the console app. So yes, the speakers you mentioned will work perfectly.
Just another thought or option: I had used the MOTU 828mkII for about one year via firewire, and I NEVER had a problem. And to answer another question of yours, it does have 2 xlr inputs as well with phantom power. I was using this in conjunction with a Windows XP P4 system.
Best of luck to you in your decision and purchase. I hope this is helpful.