Well the Chaintech AV710 does not have a headphone amp.
So it would stand to reason that a PCI sound card like the Audiotrak HD2 that has a headphone amp would be a much better solution that your AV-710.
That being said an external USB headphone amp would be an even better choice.
I just glanced at Keces.
AudiogoN ForSale: Keces DA-151
It is a DAC...I would think you would probably be better served buying something like the Fubar III...It is a USB/DAC slash headphone amp.
Firestone Audio FUBAR III USB DAC and Headphone Amp Review
Or maybe something like this.
Zhaolu D2.5a DAC & Headphone Amp
I am really not the one to recommend a USB/DAC headphone amp...But it seems that is what you need...The products that are available is just mind boggling.
But I am sure if you ask for a recommedation for a USB Head Phone Amp you will...You might want to do a search...Or just go back a few pages...There are multiple threads asking about T/Amps...USB/DAC's...USB Headphone Amp's.
I personally am looking at USB/DAC headphone amps...I have some AudioEngine 5's and Grado headphone...So I want a USB/DAC that will send analog to my A5's but will also serve as a headphone amp for the Grado's.