Sound Card for Surround Speakers

I just bought some Logitech z506 surround sound speakers to find that the rear two speakers are very quiet and the surround sound does not seem to be calibrated properly, it also needs three jacks only one of which is on my motherboard. I have decided that I am going to buy an entry-mid range sound card. I was looking at the Creative sound Blaster Recon 3D 5.1 and the Asus Xonar DGX 5.1. Which of these sound cards are best? Or are there any others I should consider as well?
Thanks Very Much.