PC or Mac Build for Media Composer (Software)

I'm looking to build either a Mac or PC to use AVID MC 4 (software). I would like a computer that allows me to edit 1080p video without additional hardware. Here are the two builds. I would love to hear what you all think.

PC

ASUS Z8NA-D6 (ASMB4-IKVM) ATX Server Motherboard

CORSAIR XMS3 12GB (6 x 2GB) 240-Pin DDR3 SDRAM DDR3 1333 (PC3 10600) Desktop Memory

Antec P183 Black Computer Case

Antec CP-850 850W Continuous Power "compatible with Core i7" Power Supply

Intel Xeon E5520 2.26GHz LGA 1366 80W Quad-Core Server Processor

PNY VCQFX1800-ELEM-PB Quadro FX1800 768MB 192-bit GDDR3 PCI Express 2.0 x16 Workstation Video Card with Elemental Accelerator - Retail

LITE-ON CD/DVD Burner - Bulk Black SATA Model iHAS124-0

Western Digital RE3 250GB 3.5" SATA 3.0Gb/s Internal Hard Drive -Bare Drive

Western Digital RE3 250GB 3.5" SATA 3.0Gb/s Internal Hard Drive -Bare Drive

Totals about $2600

MAC

Two 2.26GHz Quad-Core Intel Xeon
8MB fully shared L3 cache per processor

6GB (six 1GB DIMMs) of 1066MHz DDR3 ECC SDRAM
PCI Express 2.0 graphics NVIDIA GeForce GT 120 with 512MB GDDR3 memory, Mini DisplayPort, and dual-link DVI video output

640GB Serial ATA (3Gb/s); 7200 rpm

18x SuperDrive with double-layer support (DVD±R DL/DVD±RW/CD-RW)

$2800 (refurbished)

Thanks in advance for your help!