Yamaha DTXpress/DTXplorer/DTXtreme

I thought the DTXpress 3 allowed you to send the click to one output only..

As regards to the feeding sound into aux input an not having it come out the
main outs;
An old portastudio can be used as a basic mixer (I believe this has been
mentioned in past posts), better still a dedicated mixer will give you much
better control over the sound you want to play along to, as well as giving
you control over the modules sound (in terms of level, Eq, etc.)

I know it might mean having to 'spend money', but it will make life much
easier for you.