I just got my Sound Blaster Z today and have been putting it through its paces in Bioshock 2. Before the SBZ I was getting my surround kicks via Razer Surround feeding an Aune T1>FiiO E9>AKG Q701. The surround effect was much better than I expected, although it sounded a little closed in as far as positional accuracy was concerned. Once I got my SBZ hooked up going through the same path; Aune T1>FiiO E9>AKG Q701. I found that 100% SBX Prostudio sounded the most spacious and accurate, but all in all it was about on par with Razer Surround. Neither one, in terms of positional accuracy and surround since they're both using the same DAC/amp chain as output, sounded better than the other. I was disappointed that the performance of the SBZ, which paid money for, wasn't any better than the my free software based Razer Surround.
Then I decided to go crazy. Now my chain is Razer Surround>Sound Blaster Z>Aune T1>FiiO E9>AKG Q701. We've all heard about double amping, but what about double DSPing? Sound stage is HUGE now and positional cues are way more accurate. I have a day off tomorrow so I'll keep playing with it to see if there are any glitches or crashes, but initial impressions are incredible.