Mactec,
I think your advice blows....
I am running v wheels/rails on my y and x axis and never had one issue, so what if dust gets on the rails. Why does that matter. You need to worry about large particles and they just slide off.... Can you balance a ball on the point of a triangle?? If your so worried about the dust just place a small neodymium magnet in front and behind the v wheel, it would pick up everything instantly... (outside the box)
Joe,
Use the v-wheels/rails. Super accurate, cheap, durable, all around awesome for plasma... I would also make your own v-rails if you could. Basically its a 90 deg. angle rotated 45 deg, so the points verticle, pretty simple to machine on a mill. Its better to save your money for other things than expensive rails that are not going to benifit you in anyway. Good Luck on your build BTW....