You might want to try a cheap method first (like in post #5,) before the more expensive options. Bar position is such a personal preference thing, you really have to try it and see what works for you. (Having said that, those Roxspeed mounts would be an easy way to test forward/back positions.)
My experience is that I'm 6'2" and tried to lengthen out the "cockpit" like Z-man did. I made some bar mounts like this (post #12) except that I included sub-mount tabs for a stabilizer.
http://www.gasgasrider.org/forum/showthread.php?p=57616&highlight=+bar++forward#post57616
It felt great in the shop, but for me, in technical hilly terrain, I ended up feeling like I was "hanging" from the bars - I couldn't get my body up and over the front end the same way. Weird - it seems like the opposite should be the case. But climbing hills I had to
pull myself up and further forward vs.
leaning over the bars. I went to a sub-mount like Roostafish mentioned and am a happy guy! (mine is a Protect, but they're no longer in business.)
The point is, you have to try it and see what works for yourself. So spend $20 bucks and see what height you like before spending more $$ on something permanent (if you use a stabilizer, Roosta's idea for $129 is a good one.)
I'll send you my forward bar mounts if you want to try them out.
Jeff