Hello McReidy!
I too picked up a Yamaha DTXPLORER and it's been fantastic fun. A few months ago i bought a Roland PD-8 dual trigger pad for my SPD-S sampling pad. I have tested this on my dtxplorer by running it through the Snare input on the dtx module. The dual trigger functionality works fine, and this has allowed me to add an additional cymbal through the pad-in jack on the dtx kick pad (by using the old snare pad as a ride, and in turn the ride pad as a crash).
I am assured that it is indeed possible to have a cymbal with choke on the dtx, but i havent had an opportunity to test this functionality myself.
I bought my PD-8 pad from Billy Hyde Drumcraft in Surrey Hills, Sydney, however, because i bought it in conjunction with several other items, it was discounted (i think it ended up costing about 80 dollars?). As for electronic choke cymbals, I'm not sure how expensive these would be.
If you get an opportunity, drop by my youtube page and check out the dtx /w the spd-s and pd8 sampling pad!
Cheers,
Josh
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Check out some of my drumming!
http://www.youtube.com/profile?user=JoshKoen