Lately, I've been thinking about getting a dedicated sound card. This RealTek onboard chipset is okay, but I'd prefer something that's GREAT or AWESOME. So, I have a few questions.

1.) Is EAX in supported games as exciting as they'd like people to believe?
2.) Would having a dedicated sound card improve my framerate in games?
3.) Are PCI (not PCI Express x1) sound cards fairly decent? My motherboard has one free PCI slot and one free PCI Express x1 slot but the PCI Express slot is covered up because my graphics card is dual-slot wide.
4.) What brands of sound cards are worth it? I've found great reviews on Sound Blaster Audigy series and Omega Striker sound cards, but I really don't know much.

I'll be using 5.1 analog outs for my Logitech X-540 system with the sound card, if that matters.

And purely for my curiosity but unlikely to factor into the above:
5.) Can HDMI be used solely for audio out while VGA or DVI is used for the display?

Thanks for any help!