What soundcard would you recommend for a 5.1 channel system? It does not matter whether it is PCI or PCI-E.

I have read good reviews about Asus Xonar Essence XTX. but also have read that it is geared for headphones and some have experienced problems with 5.1 digital sound.

Can a 5.1 channel system be "converted" to a 7.1 by adding two speakers?

as far as the converted question... i don't think so.

maybe get a bigfoot killer nic and sound card in one? http://www.newegg.com/Product/Product.aspx?Item=N82E16833189002&cm_re=bigfoot-_-33-189-002-_-Product didn't find the one i'm thinking of. think it uses an asus xonar product.

I've heard very good things about the Auzentech Forte and Bravura when it comes to surround sound. Their cards are technically based on Creative's, but lack Creative's "$h!acular" driver support.

Asus' ST/STX are geared towards stereo sound and headphone use. Their drivers do leave something to be desired, although the sound is excellent. But I would not recommend them for surround. The Asus D2X is the high-end surround card, but it seems they also have some driver issues.

One of the best places to go for this sort of info in HardwareCanucks: http://www.hardwarecanucks.com/forum/audio/

In the first few pages, you should find some good information on what suits your needs best.