I need your opinion. Is the xp3000 worth twice the price of the xp2700???
Absolutely not.
All of the XP/Barton processors currently on the market have limit at about 2.2 GHz, 2.3 GHz with increased voltage beyond 1.65V and air cooling. 512 L2 cache for Barton means only about 3-4% better performance than your standard T'bred.
Personally I think the best to buy is XP 2100 which is about $60-70, and you can get B revision at newegg. That CPU will be easy to overclock. Performancewise overclocked to 2.2 GHz it is close to Pentium 2.8 B which is no small feat, considering the price of the Northwood.
Shortly: no AMD processor is worth more than $70, that is the price of B revision of XP 2100 or DLT3C XP 1700.
I have two Bartons 2500, three B XP 2100, one B XP 1700 DUT3C. They are all about the same value, as far as I am concerned, all overclocked to 2.1-2.2 GHz.
None of them can hold a candle to my Intel 2.4C @3.0 GHz by a long shot.