Sound Cards and confusion

What speakers will you be using?

added answer to original post

SteelSeries Siberia V2 Pro Gaming has it's own included USB soundcard to create the Virtual Surround effect.
You wouldn't need a separate sound card.

not getting the usb one

I should make a note: Aside from the PCI->PCI-E bridge chip on the DX, the ASUS Xonar D1/DX should be essentially the same card.

Also, the ASUS D1/DX and HT Omega Striker use basically the same C-Media chipset, which is why the have most of the same features. HT Omega offers DTS encoding over the SPDIF port (which it sounds like you aren't using; The D1/DX only offers Dolby Digital encoding), where the ASUS cards offer EAX 5.0 emulation. The cards are VERY simmilar, all things considered.

Personally, Its between ASUS and HT Omega; Creative simply doesn't have anything to offer besides "true" EAX compatability, and if that matters, you might want to look at the Auzentech Prelude (which should be around the price of the Titanium).

Out of the ones you listed I would get the titanium. I have used one for about a year now and I must say the sound quality is great and it is packed full of features but for you since you will be using headphones IMO I wouldn't pick any of them. For using high quality big driver power hungry headphones you need a card with a powerful headphone amp.

Cards that off headphone amps.

HT Omega Claro
http://www.newegg.com/Product/Product.aspx?Item=N82E168...

ASUS Essence STX
http://www.newegg.com/Product/Product.aspx?Item=N82E168...

Auzen also makes a few cards with great headphone amps too go to their website to find them since newegg does not carry them.

Read this thread the other day but i'll chime in now to include the Auzentech's to supplement SAAIELLO's suggestions which are considered the best available.
The Auzentech's are by no means as good as his suggestions but definitely better than your consideration list and affordable.
AuzenTech Forte Low Profile PCI-E 7.1 Sound Card PCI-E Dolby Digital Live Headphone AMP
http://www.ncixus.com/products/35596/AZTXFF7105551/Auze...
AuzenTech Bravura PCI-E 7.1 Sound Card X-FI EAX DTS Neo DTS Interactive Headphone AMP
http://www.ncixus.com/products/49090/AZT-BRAVURA/AuzenT...
The Forte at that price is a very good deal much better then the Bravura which was on sale at NCIX less then a month ago for $75.
The Forte is also the next card up from the Bravura in Auzentech's line-up.

They're all good cards, (with the exception that I have a hatred of all things Creative). The HT Omega has the best headphone amp.

I don't think any headphone amps are required to drive the pc-350..

After a little research, it seems like though the PC-350 will work amazingly without any dedicated amp, having the input feed through an amp will significantly enhance the audio.. So its more like a headphone amp is not necessary to drive those headsets but It'll help improving the audio expreshence.. So considering that, i too would recommend the Asus Xonar Essence STX..

pc 350 has resistance of 150ohms

pc 360 is only 50ohms

Its impedance, not resistance.. The PC 350 has two impedance parameters though.. One for the microphone and one for the sound channels.. I guess the microphone has a higher impedance parameter for providing clearer voice chats..

impedence is the measure of resistance in an alternating current... (resistance that varies according to frequency)

resistance applies for both AC and DC.