Can i crossfire my ati 5770 with possibly the 5850,5870,or 5970



Sorrry if its a stupid question ,but this is my first build so dont really have any prior knowledge about pcs.Also if i were to crossfire with 5770 oc would it be somewhere around the performance of the 5870 dunno just curious is all.Or should i just wait for nvidia's hyped up fermi gpu.

Processor([== Quad Core ==] AMD Phenom™ II X4 965 Black Edition Quad-Core CPU) 4.0 ghz oc 68c
Processor Cooling(Thermaltake MaxOrb CPU Cooling Fan System -
Memory(4 GB [2 GB X2] DDR3-1800 Memory Module - Corsair
Video Card(ATI Radeon HD 5770 - 1GB
Video Card Brand(Major Brand Powered by ATI or NVIDIA)
Motherboard(ASUS M4A785TD-V EVO -- AMD 785G Hybrid CrossFire Chipset w/8-ch HD Audio, Gb LAN, S-ATA Raid, USB 2.0, 2 PCI-E MB)
Power Supply(800 Watt -- Power Supply - SLI Ready)
Primary Hard Drive(750 GB HARD DRIVE -- 16M Cache, 7200 RPM, 3.0Gb/s - Single Drive)
Data Hard Drive(None)
Optical Drive([8X Blu-Ray] LG BLU-RAY Reader, DVD±R/±RW Burner Combo Drive - Black)
2nd Optical Drive(None)
Flash Media Reader/Writer(12-In-1 Internal Flash Media Card Reader/Writer - Black)
Floppy Drive(None)
Sound Card(3D Premium Surround Sound Onboard)
Network Card(Onboard LAN Network (Gb or 10/100))
Operating System(Microsoft Windows 7 Ultimate

You cannot crossfire a 57xx GPU with a 58xx GPU, but you can buy another 5770 and crossfire it with the one you have now to get performance similiar to a 5870.

If your pockets are REALLY deep and your not happy with the performance of your 5770 then wait for Fermi.
Although I'd recommend you get another 5770 as a cheaper way of boosting performance.