If you want dynamic, swirling pads or soundscapes, with or without rhythms or sequences synced to your host BPM, you'll have a hard time finding a better synth than this. There are a number of synths that excel at this kind of thing, and this one is right up there with the best of them. If you're familiar with H.G. Fortune's synths (Protoplasm, STS-21, Swamp), you'll be right at home with Golden ASET, as it was originally developed by H.G. Fortune as the ASET 2121 MythoSpheric Space Synthesizer.
Golden ASET comes with four 128-soundset banks, for a whopping total of 512 presets, all designed by sound and graphic designer Vera Kinter. These provide a wide selection of pads, soundscapes, and FX, which is what this synth is designed for. (You should look to other synths if you want a lot of bass, lead, and simple sound presets.) The rich, dynamic sounds result from four oscillators (two analog style and two PCM wavesample), two LFO's, Sample & Hold, a vLFO (very low frequency oscillator) which can be used to modulate the LFO's or S&H, two filters (one for each pair of oscillators) each with its own envelope, and programmable pulse width for the square wave. The delay feedback amount can also be modulated by the vLFO, S&H, or LFO1. This is a cool feature which provides for automatic varying of the delay repetitions over time. Also included are the famous H.G. Fortune "lazy" buttons, which allow random selection of various parameters by just pressing a button. Modulation options are extensive, with the LFO's, S&H, and onboard delay syncable to host BPM, and routable to a variety of destinations via a clear, accessible set of GUI controls.
And speaking of the GUI: this one is a work of art. If there were an award for best VSTi GUI, this one would get my vote. It manages to be beautiful and highly functional at the same time. If you've used H.G. Fortune's synths, this GUI will look familiar (with the addition of Egyptian hieroglyphic graphics) because Vera Kinter (who designed the GUI's and many of the presets for the H.G. Fortune synths) designed the GUI. She also has a number of excellent GUI controls available to other developers for free on her website.
For $30, complete with 512 presents and manual, it's a steal.