Good deal on ATI 5850? Crossfire compatible with mine?

I can get an "ATI Radeon HD 5850 1GB DDR5 Graphics Card With 1080p HD-3D HDMI Port, Display Port & DVI Port + Fan Cooler!" for $120. I already have a Sapphire 5850 that I bought in January of 2010. Can I Crossfire these two even if they are different brands, they seem to have the same specs, I've just never had more than one GPU... I know I don't "need" to do this but I figure if I can get one cheap before they stop making them I'll be set for a few years. Here are my specs:

Intel Core i5-750 Lynnfield 2.66GHz LGA 1156 95W Quad-Core Processor BX80605I5750

CORSAIR CMPSU-750TX 750W ATX12V v2.2 SLI Certified CrossFire Ready 80 PLUS Certified Active PFC Compatible with Core i7 ...

Intel X25-M Mainstream SSDSA2MH080G2R5 2.5" 80GB SATA II MLC Internal Solid State Drive (SSD)

Microsoft Windows 7 Home Premium 64-bit 1-Pack for System Builders - OEM

ASUS P7P55D-E Pro LGA 1156 Intel P55 SATA 6Gb/s USB 3.0 ATX Intel Motherboard

G.SKILL ECO Series 4GB (2 x 2GB) 240-Pin DDR3 SDRAM DDR3 1600 (PC3 12800) Desktop Memory Model F3-12800CL7D-4GBECO

Seagate Barracuda 7200.12 ST3500418AS 500GB 7200 RPM SATA 3.0Gb/s 3.5" Internal Hard Drive -Bare Drive

SAPPHIRE 100282SR Radeon HD 5850 1GB 256-bit GDDR5 PCI Express 2.0 x16 HDCP Ready CrossFire Supported Video Card w/ATI Eyefinity

THANKS