Why would one even consider an AV78X (Via KT400) when the vastly superior A7N8X (Nvidia nForce 2) exists? The nForce 2 defeats the KT400 in every single benchmark, has far better integrated audio (which is actually a viable threat to an Audigy/Santa Cruz), and is much more stable. The A7N8X is also compatible with the upcoming 400MHz FSB Barton. The price difference between the two motherboards is also negligible nowadays. If you're going the AMD route, pick up an Asus A7N8x; it is the best single-CPU AMD motherboard available at any cost.
Drives I Own:
Asus S520/A, Plextor UltraPlex 40TSi, Lite-on XJ-HD166S, Pioneer DVD-106S, Toshiba SD-M1712, Plextor PX-R820Ti, Plextor PX-W1210TS, Plextor Premium, Samsung SM-352B, Teac CD-W540E, Yamaha CRW-F1, Plextor PX-708A, Sony DRU-510A