AMD have just introduced the Phenom II X4 980 Black Edition, which is a multiplier-unlocked 3.7Ghz 45nm quad-core processor with a $195 USD retail price.
AMD's fastest quad-core to date is clocked at 3.7GHz and aims to compete with Intel' sSandy Bridge CPUs. It comes with 6MB of L3 cache and thermal design power (TDP) of 125 watts. The Black Edition label means that the CPU's multiplier is unlocked, which eases overclocking.
According to the first reviews of the new Phenom CPU that have appeared online, the Phenom II X4 980 performs slightly better than its quad-core Phenom predecessors, but it can't hang with a new Intel Sandy Bridge processor like the Core i5-2500, even when overclocked.
Considering that the new AMD quad-core is priced at $195 and the Core i5-2500 is a mere $15 more (and Core i5-2500K is $30 more), there doesn't seem to be much reason to build a new desktop around the Phenom II X4 980, though you might consider it if you want to upgrade an existing socket AM2+ or AM3 system.
Furthermore, you can buy a six-core Phenom II X6 1090T processor for $5 more.