I don't know if you can get them for less than $200, but I know that I owned a Threshold once, and it was quite the interesting marker. I eventually sold it, but for the time that I had and used it, I was impressed, especially considering it came from Dangerous Power.
At one point I also owned a Quest, and I have to agree with Fallinher0 that it was a nice littler marker. Again, I don't know what they're going for nowadays, but if they're less than $200, they'd be a nice choice too.
As for a DM3 or an earlier model of the Matrix, sure, they might be decent markers in terms of performance, but honestly, I don't know as I could ever used one simply because of their ergonomics in comparison to the markers of today... I mean, think of the weight and the bulk of one of those markers in comparison to the current Matrix models, the current EGO, etc.