Yamaha DTXpress/DTXplorer/DTXtreme

Ok...I'm a little cornfused here! Inputs 1-8 on the back of the 
module are stereo...L-Pad...R-Rim. Correct? Does this mean if I want 
to add more pads that I just use a stereo input adapter plug? EX: I 
tried to use a 1/4 stereo plug and I placed it into Input 2. I then 
branched off to my Normal Snare..and then one to Hi-Hat. It shows 
trigger input from snare (pad2), but not hi-hat pad (which I thought 
it would be the rim2 input). IF I reverse the wires..naturally it 
shows the other way around. All its looking for is a trigger input 
right? Is there something I am suppose to do in the setup of the 
module? I guess in short I'm asking..whats the difference in buying a 
stereo cymbal..etc.,. with rim capabilities and me just adding other 
pads via channel 1-8? I'm trying to build a monster kit here! lol. 

Thanks In Advance,

Gary 

P.S. If I can add on 1-8 with pad1,rim1,etc.,. then wouldn't that 
give me a total of 16 inputs? Plus 9/10. Makes 18..not counting the 
hi-hat pedal..etc.,. About 24 total isn't there?