Processors are they any good?
If it fits in your existing motherboard, then it's a no-brainer. Yes! If it would mean buying a new board, then you should really be looking for a motherboard in which you can stick a reasonably priced processor (low-end Athlon, Sempron) right now and one that's twice as fast in two years.
It's silly to buy "fast" processors unless you really need that power. The power/price ratio is too low. As a rule of thumb, if you want a kickass machine, buy the second fastest of everything available (CPU, video card etc.). It will cost half the price of the fastest with little difference in performance. If you want the best performance for your money, look to top-end budget processors (Sempron, Celeron) or the slightly faster, lower end flagship processors (Athlon, Pentium).
Any of these processors is more than up to the job unless you're into 3D CAD or a serious gamer (where video card is much more important--and expensive--anyway). If you take care when choosing the motherboard, you should find that you can stick a low-end Athlon in today for most satisfactory performance, and then in a year and a half, you can upgrade to a faster Sempron. Both combined will cost the same as buying a fast Athlon now, but give you a slightly slower computer now and a much faster one in a year and a bit.