No all your RAM should be the same size, type and latency for optimal addressing. I wouldn't recommend using different sizes these days. Treat yourself, go for 4 gig.
The gigabyte @BIOS utility is a pretty simple thing to use just make sure you don't have anything else running when you do it cos it'll be a hell of a biyatch worse to sort out if another program decides to use all your CPU and @BIOS can't finish the flash.
Sometimes gigabyte don't put the BIOS on their website but @BIOS can pick it up off the update server, you should probably try that.