One thing to consider - the Sargent ships with Carbon FX material cover. And that is really slippery. You have to buy DTX covers from Sargent, and those will cost another 100 USD each - I believe (I paid UK prices, so don't know about US ones).
Maybe if you buy new, you can specify to have DTX fitted, and then there would be no extra costs. I bought the backrest new, specified for DTX, and had no extra cost.
The DTX covers are both nicer and more comfortable than the Carbon FX. I have no idea with they ship the seat with those covers, as standard - I would have sold my Sargent seat, if I couldn't fix the slipping problem.