NewEgg has the HP MediaSmart EX485, Intel Celeron 2.0 Ghz 2GB 750GB Mac Compatible, Powered by Windows Home Server - Retail for only $400 + $0 shipping = $400 shipped. Tax in CA, NJ, TN.

Buy it together w/ Seagate Barracuda LP ST31000520AS 1TB 5900 RPM SATA 3.0Gb/s 3.5" Hard Drive via this combo for only $405 w/ free shipping.

Update: Extra $20 off via coupon code SERVER1135

NewEgg has the AMD Athlon II X2 240 Regor 2.8GHz 2 x 1MB L2 Cache Socket AM3 65W Dual-Core Processor - Retail for only $60.00 + $0 shipping = $60 shipped. Tax in CA, NJ, TN.

Buy it together w/ GIGABYTE GA-MA785GM-US2H AM3/AM2+/AM2 AMD 785G HDMI Micro ATX AMD Motherboard via this combo for only $120 w/ free shipping.

NewEgg has the Athlon II X2 2.8GHz CPU combo for only $250 - $15 rebate + $0 shipping = $235 shipped after rebate. Tax in CA, NJ, TN.

Combo includes:
AMD Athlon II X2 240 Regor 2.8GHz Socket AM3 65W Dual-Core Processor Model ADX240OCGQBOX
GIGABYTE GA-MA785GM-US2H AM3/AM2+/AM2 AMD 785G HDMI Micro ATX AMD Motherboard
Seagate Barracuda 7200.12 ST3500418AS 500GB 7200 RPM SATA 3.0Gb/s 3.5" Internal Hard Drive
CORSAIR DOMINATOR 4GB (2 x 2GB) 240-Pin DDR2 SDRAM DDR2 1066 (PC2 8500) Desktop Memory Model CMD4GX2M2A1066C5