You asked earlier and I see that I never responded ... But I am running on windows. I am guessing that OSX Aggregation is a Mac only thing... I honestly know nothing about them.
Yep, Device Aggregation is the name for a specific OSX feature.
Have you installed the USBPre2 ASIO drivers? They include low level WDM drivers and if you select the WDM drivers in Smaart you may see both devices inputs. Depending on your version of Windows ASIO4ALL may or may not work, it hasn't been supported in 6 years or sound back when I looked at it a decade ago it was hit or miss.
http://www.harmonycentral.com/articles/aggregating-audio-interfaces-w-30956616 If you want to invest more time in getting this to work, contact Sound Devices, and also make a post on GearSlutz' recording forum, I think you are more likely to find someone who has tried to solve aggregation under Windows in a recording forum. On Mac's its been a built in feature for many releases, and doesn't always work perfectly.