2.4, 2.5, or 2.8 GHz will all offer you a comparable level of performance and will all last to around the same age, the benchmarks may go up as the models increase, but the difference is negligible in real life. Unless you're constantly bumping up against the limits of a processor, I wouldn't really recommend going with the next step up... but that's just me speaking. Personally, I go with the highest I can afford because it makes the computer feel psychologically faster to me (tell me that didn't sound crazy) even if in reality I have no base to judge my perception on and there really isn't a difference made in 90% of my general computing tasks. So basically, unless you're like me, just go for the base model and upgrade your hard drive and RAM.