Bonz, don't forget that the processor will not output the LFE from the front outputs, unless you switch it to "no sub", which will kill the LFE output. I would run the processor with "no sub" selected, and wire your two subs to the front channels in stereo, one channel to each sub.

With "no sub" selected, the LFE track will be added to the front outputs (set to "large", of course) in mono, and the left and right main channels' bass will be reproduced in stereo at the same time. This is how I run my Def Tech's with built-in powered subs.