I just picked up an Emachine with an Athlon XP 1600+ for a friend. It was $599 after rebate at BestBuy. He already had a Geforce 3, so we just popped that in and he had a decent system. It was a few hundred bucks cheaper than a newegg 1800+ system I speced out for him and it will save me a lot of support hassles...
http://www.emachines.com/products/products.html?prod=eMachines_T1600
Specifications
CPU: AMD Athlon? XP processor 1600+ (QuantiSpeed? architecture)
Chipset: VIA KM 266
Memory: 256 MB DDR (PC 2100)
Hard Drive: 40 GB HDD
Optical Drives: 24x10x40x Max. CD-RW Drive;
3.5" 1.44MB FDD
Video: S3 ProSavage8 (integrated)
(1 AGP slot available for upgrade)
Sound: AC '97 Audio
Modem: 56K* ITU v.92 ready Fax/Modem
Network: 10/100Mbps built-in Ethernet
Ports/Other: 4 USB ports (2 on front), 1 Serial, 1 Parallel, 2 PS/2, Audio In & Out, MIDI/Game port, Mic-In & Head Phone jack on front, 3 PCI slots (2 available)
Peripherals: Keyboard, Wheel Mouse, Amplified Speakers
Dimensions: 7.25"w x 14.125"h x 16"d