which to buy?

So, I am going to get a 8600gt graphics card and I wanted to ask is there any difference between manufacture brands (or how do you call them). I can either buy Asus EN8600GT/2DHT/256M ( http://www.asus.com/products.aspx? [...] delmenu=2), XFX PV-T84J-UDF3 ( http://www.xfxforce.com/web/product/...920#openLarger), Sparkle SF-PX86GT256D3 ( http://www.sparkle.com.tw/product_ [...] ub_id=110) or Innovisio 8600GT-G5F3CD ( http://www.inno3d.com/products/gra [...] 00gt.htm). They all have the same GPU and memory speeds and the same gddr3 memory. Is there a difference then it comes to over clocking? And another quick question, will I be able to put my vf700 cu on 8600gt? All your opinions are welcome.