Can anyone recommend a piezo system for installation in a Martin DXM acoustic guitar? This is a Made in Mexico Martin, so I don't want to spend too much, maybe around $100??

Dave, it really depends on what you want to spend. AXL, an inexpensive gear company, makes an acoustic pickup you can find on eBay for around $25. Dean Markley also makes an inexpensive transducer for around $35. Then again, if you're looking for great sounds, you can go all the way up to $300 or probably more. Check out offerings by Fishman, Shadown, LR Baggs, and others.

Fishman makes a nice model right around $100, I believe.. check this out:

http://accessories.musiciansfriend.com/product/Fishman-NeoD-Magnetic-Soundhole-Pickup?sku=303160

Anyone else that has an opinion, please feel free to post..

Just to throw it out there, mate, even if you're only looking for something around $100, it's still a great help, I think, to keep checking out gear that's WAY out of your price range, so you understand what high end gear sounds like. The same holds true for low end gear. You begin to understand what kind of sounds are out there, and you can hone in what kind of sound you want better before the search really begins. You start to understand where to look and what brands typically sound like.

I've bought a lot of stuff on ebay, including musical equipment. As was mentioned above, check there for what you want before you purchase it new. And craigslist is another great place to search for something specific and not have to pay full price.