I've been running a LanParty CR3200 Crossfire board with an AMD Athlon 64 X2 4400+ running at 2.2 ghz, with 2 Gig of DDR400 RAM, and a pair of VisionTek Radeon X1600 XT cards in crossfire mode.
I have to say, the lanparty board is the most unstable POS I have ever owned.  I'll never buy another of their products.. Well.. never is a long time, but it'll be a freak accident if I do.  The system is so unstable I've considered starting over from scratch, maybe going back to Intel & Nvidia, but I hate to blow that much cash.
So.. I decided to buy a board on eBay, and stay with my 939 chip for another year or 2.  I was going to buy an Asus MVP 939 crossfire board, but those things are going for gold.  I was outbid for one at $122.50 by a last second sniper.  I then found a factory refurbed Abit AT8 32X Crossfire board that I was able to pick up for $50.  In factory configs, it is almost a clone of the Asus board, and I am not an over-clocker, so that suits me just fine.
While I was looking online, I was able to pick up a couple of VisionTek Radeon HD 2600 XT video cards with 512 of DDR3 RAM for about $100 each.  All-in-all, with those cards in crossfire mode, this should be a fairly impressive upgrade for $250.
Here are the specs:
Abit AT8 32X Socket 939 AMD - ATI RD580 Based AMD Athlon 64X2/FX/64 Main boards, 2000MT/s HT, Dual DDR400, ATI CrossFire, SATAII 3GB/s, GbE LAN, IEEE1394, ABIT Silent OTES II. Exclusive ABIT Engineered motherboard technology designed for unprecedented power, convenience, and control over your PC. 
Processor
- Socket 939 for AMD Athlon 64X2/ 64FX/ 64/ Sempron Processors
- 2000MT/s System Bus
- AMD CPU Cool ‘n’ Quiet Technology
Chipset
- ATI Crossfire Xpress 3200 + ULI1575 chipset
- Support Dual Full PCIE x16 bandwidth to graphic
Memory
- Four 184-pin DIMM sockets 
- Supports dual channel DDR400 ECC/non-ECC un-buffered memory 
- Supports maximum memory capacity up to 8GB
Graphics
- Two PCI Express X16 slots support Dual Graphic card by ATI CrossFire Technology
- Two X16 graphics links for high performance Crossfire configurations
ABIT Engineered
- ABIT uGuru Technology
- ABIT Silent-OTES Technology
Audio
- On board 7.1 Channel HD Audio CODEC
- Support S/P DIF In/Out
- Dobly Digital Live technology
GbE LAN
- On board 10/100/1000M PCIE controller
Serial ATA
- 4 x SATA 3.0 Gb/s (RAID 0/1/0+1/5) 
- Supports SATA AHCI, providing native command queuing and native hot plug 
- Dual on board Silicon Image Sil3132 PCIE SATA 3Gb/s RAID controller
IEEE 1394
- Supports IEEE1394 by PCI controller
Expansion Slots
- 2 x PCI Express X16 slots
- 2 x PCI Express X1 slots
- 2 x PCI slots
Internal I/O Connectors
- Floppy Port supports up to 2.88MB
- 2 x Ultra DMA 33/66/100/133 Connectors
- 6 x SATA 3.0 Gb/s Connectors; 2 x USB headers, 1 x IEEE1394 header
Back Panel I/O
- 1 x PS/2 Keyboard, 1 x PS/2 mouse
- Silent OTES, 1 x S/P DIF Output, 1 x S/P DIF Input
- 7.1 CH Audio connector (Front, Line-in, MIC-in, Center/Subwoofer, Surround, Rear Surround)
- 4 x USB2.0, 1 x IEEE1394, 1 x RJ-45 LAN Connector
Dimension 
- ATX form factor 305 x 245mm (12 x 9.6 inch)
Package Content 
- Abit AT8 32X Motherboard
- Back Panel 
- IDE Cables
- SATA Cable
This motherboard has been factory reconditioned and will be shipped in an original box. 
VisionTek HD 2600 XT
512MB GDDR3 
Optimized for DirectX® 10 and Windows Vista™ 
CrossFire™ multi-GPU ready 
ATI Avivo™ HD video & display technology 
Hardware processed HD video acceleration (UVD) 
Full HD 1080p video playback 1 
Built-in HDMI2 for one-cable audio and video connectivity 
5.1 (AC3) surround sound 
HDCP ready for Blu-ray and HD DVD playback3 
ATI Catalyst™ software suite 
CrossFire™ HD Gaming Technology
Add a second card and really get your game on! 
Easy plug-and-play internal connector system 
HD Video Technology
Connect to your big-screen TV for massive entertainment! 
Built-in HDMI with multi-channel 5.1 surround audio 
1) Require 1080p HD capable display 
2) May not support all HDMI displays. Please visit AMD Customer Care at ati.amd.com for more information.
3) Playing HDCP content requires additional HDCP ready components, including but not limited to an HDCP ready monitor, Blu-ray or HD DVD disc drive, multimedia application and computer operating system. 
RECOMMENDED SYSTEM REQUIREMENT
PCI Express® based PC is required with one X16 lane graphics slot available on the motherboard 
400 Watt (550 Watt for CrossFire™) or greater power supply recommended 
Certified power supplies are recommended. Refer to 
http://ati.amd.com/CertifiedPSU for a list of Certified products 
1GB of system memory 
Installation software requires CD-ROM drive 
DVD playback requires DVD drive 
Blu-ray / HD DVD playback requires Blu-ray / HD DVD drive 
To complete the CrossFire™ platform, a second ATI Radeon™ HD 2600 XT graphics card, a CrossFire™ Ready motherboard and one CrossFire™ Bridge Interconnect cable per board (included) are required 
WHAT'S INSIDE BOX
ATI Radeon™ HD 2600 XT graphics card 
CrossFire™ Bridge Interconnect 
DVI to HDMI adapter 
DVI to VGA adapters 
HDTV Component out adapter 
Video-out adapter 
Set-up CD 
Manuals 
OPERATING SYSTEM
Windows Vista™ 
Windows® XP 
Windows® XP x64 Edition 
Windows® Media Center Edition 2005 
DISPLAY SUPPORT
Two Dual-Link DVI-I connectors for high-resolution digital displays 
ATI Radeon™ DVI-I to HDMI2 with 5.1 audio (adapter) 
HDTV Component (YPrPb) output (adapter) 
VGA mode support on DVI-I outputs (adapter) 
Drive two displays simultaneously with independent resolutions and refresh rates4 
TV output requires HDMI, component, S-video or composite cable (not included) 
DISPLAY MODE
Digital Displays (Connected by DVI) 
All Resolutions up to 2560x1600 
Analog Displays (Connected by VGA) 
All resolutions up to 2048x1536 
TV-out 
SDTV (analog): 480i | 525i 
HDTV (analog): 1080p | 1080i | 720p | 480p | Ccustom resolution3 
HDTV (digital): 1080p | 1080i | 720p | 480p | Ccustom resolution3 
Note: Resolutions are limited by the performance of the attached monitor.