Sound card for synthesis/sampling/audio

Okay, my turn to ask for help. This is one area where I'm in *way* over my head.

I need a new sound card for synthsis, sampling, and general audio. Obviously, better sound quality is a plus, but I don't need (quitre) audiophile sound. I want to do software syntheisis in real-time, so ultra-ultra-low-latency ASIO 2.0 and DirectSound drivers are absolutely necessary. Independantly routable sound channels would be a plus. PCI-E would be preferred. And finally, good sound quality is nice too. If the X-Fi Crystallizer is not a gimmick, that would be a plus too. Obviously, this is for my studio computer, it will see little, if any, gaming or movie playback, but good quality music playback would be good. I would prefer if I didn't have to crawl around to switch from headphones to my amp to my half-blown Logitech Xtrusio speakers, and my case has no front-panel audio jacks.

Yes, but my budget is rather tight. I was considering the X-Fi Titanium, Extreme Audio, or Forte, as well as the Xonar Dx1 or Dx2. The absolute upper limit of my budget is ~$150, but I'd like the cheapest card I can 'get away with'. I am of course willing to consider cards other than the few I mentioned.