Feb 23, 2008 01:51 pm M-Audio (I use the Delta44 4in/4out and the UNO for midi) makes some PCI cards in that price range. Mainly a matter of how many simultanious inputs you need, their Vista 32bit driver is solid.
As for optimizing Vista definitley uninstall all the junk software that comes with a new computer and better yet if you can do a fresh install of Vista without installing all the junk software that's the best route, but most off the shelf PC's recovery disks won't give you that option however.
Turn off Media Center and disable the Media Center services (don't confuse with Windows Audio or Media Player services). That's about all you should need to do. You can turn off Aero/Themes etc, just like XP but in my tests there is very little if any thing to gain doing so.
Dan