Would it be a waste of money to buy the Sound Blaster Audigy 2 ZS Platinum Pro sound card for use with a Harman Kardon HK395 speaker set ??

or would the sound quality be much better than the one produced by the integrated sound card (obviously referring to the speakers here..no doubt the soundcard is way better)?

You shouldn’t need anything other than an onboard sound card. That speaker set just connects with a normal stereo line out. I have an Audigy basically to do 6-channel output to my surround reciever, which my motherboard doesn’t do on its own. The AOpen board you were looking at has a pretty good audio chipset. Unless you have something specific in mind or really want a LiveDrive, you can pass on it.

Thanks, I’ll buy it when I have a set of speakers which can make full use of it