I'm not an expert on the Xilent like basslines, but I do have some experience with the "swirling" ones you talked about.
Here's a picture of the reese bass used in my BP track Everfree.

As you can see this is really basic, there's some chords in there aswell and a shriek sound to make it a bit more interesting.
This is what it sounds like:
https://dl.dropbox.com/u/52883961/MLR%2 ... tering.mp3Not that great right? I mean there is already some movement in the reese bass thanks to phasing and detune but it still sounds a bit boring.

That's where this baby comes in. I put a LP filter on the reese out channel and created an automation clip in FL to control the filter.
This is what it sounds like now:
https://dl.dropbox.com/u/52883961/MLR%2 ... tering.mp3That's a lot better already, we get a lot of movement in the sound thanks to the stabby LP filter automation.
I added a little pitchbend down at the end here:
https://dl.dropbox.com/u/52883961/MLR%2 ... 20down.mp3Okay so the basic reese bassline is done. Now just add some good drums and a subbass and we've got ourselves a track!
https://dl.dropbox.com/u/52883961/MLR%2 ... 20beat.mp3This is just one of the many ways to make a reese bass more interesting. There are a lot of neurofunk producers that resample their reese to mess around with it, chop it up and reverse parts. I know guys like Xilent and Receptor create a single bass stab and copy the VST a couple of times to create different reese stab sounds. You can also mess around with automation on different kinds of filters and parameters.
I hope any of this helps and good luck creating awesome reese basslines!