Hi ambientvalent,
If you post the link to the rack and not have it on private, it will show up on the forum as an image and interactive, so that we can see the module descriptions.
For simple attenuators you can use the Mixup and Amps modules that you currently have.
I think that if I owned this and wanted to make ambient, I would either add a second oscillator with a different flavour, or a second filter. You have a lot of nice utilities that have more 'modulation outs' available than you need for just the Atlantix. Most (self-oscillating) filters and oscillators can be slowed down far enough to work as LFOs as well.
Atlantix has two oscillators, a second oscillator module could complete a 3-voice chord. Or use it on it's own when you don't feel like Atlantix for a day. For different flavour oscillators you may think about:
- ALM MCO2, it has digital libraries like wavetable and physical modeling and a built-in filter and envelope and is only 6 HP. Most of its controls are in menus though.
- Famous Plaits in a 6HP clone version, has digital libraries and a low-pass gate. No real filter and there's only one filter in your system so far.
A second filter can be used on the second oscillator of the Atlantix, or use the Atlantix filter and the second filter in series or parallel. I would either choose something that can also track 1v/oct and self-oscillate so that you can use it as an oscillator+lfo, or maybe an Oberheim style state variable filter (which will traditionally not self-oscillate) as it can move between filter types fluidly, great for ambient.
If you stick to 6 HP, you can use that last 2 HP to get an extra utility of your choice in.
Hope that helps, good luck!