To all those who pointed out my guiminer problem was because I had all three miners pointed at the same gpu, you were right - I was
smart enough to set the GTX 480's up correctly but forgot to check the same when I cloned 2nd & 3rd gpu from my first 7870 miner.
guiminer connects to stratum.bitcoin.cz:3333 ok, and all three are putting out 360+ MH/s.
I'm happy that you're getting 360+ MH/s on your Asus HD7870DC2-2GD5-V2 gpus. The Fedex dude was just here a couple of hours ago to deliver two of exactly the same cards that you have to replace a couple of mining-challenged Nvidia GPUs on an old gaming rig. I have come to the conclusion that generally, AMD cards that are moderately OC'd, usually hashes around 26% of the number of stream processors. So I figured that I would be getting around 265 MH/s (26% of 1024 stream processors) out of each of these cards. At what clock are you getting 360+ MH/s with and which AMD CCC version are you using, may I ask?
Edit: Oops! Never mind. My old eyes betrayed me. You got the HD 7870s; I got the HD 7850s. I got excited over nothing. :-)