You should be able to notice a difference regardless, but I think it really depends on what you use your system for. As far as the TBred 2600/Barton 2500 goes, I'm going with the 2500 Barton because for one, it's cheaper, and two, it has more cache than the 2600. I really just wanted the 333MHz FSB and when I discovered that the 2500 Barton was cheaper than the 2600 TBred -- I'm all for that.