Well, I guess I'm a little bit soured on my experience with crossfiring videocards. I learned a lot about what the potential obstacles (which in the end are my fault) but it's brought me to a crossroad of spending more money to fix the situation.
About 3 weeks ago, I saw a deal for an open box 4850 for $77 on newegg. This was shortly after I had purchased a brand new 1080p monitor. I quickly pulled the trigger as I've read that a crossfired 4850's performance is surprisingly good for 1080p at under $200 and since I was already running a 4850 already, I figured it would be a no brainer upgrade. Anyways the card arrives, and initially things are okay as I run through some of my usual games (Borderlands, Torchlight, TF2, L4D, Crysis) and it seemed to run fine. The only issue I saw was that the temperature was a little on the high side with the new card (which was the card on top). I assumed it was the stock cooler so I ordered an Accelero S1 Rev2 to rectify that after my PC locked up while running the character creating for DA:Origins (I figured it was a temp issue as the new card ran 20C higher than the old card- didn't realize that card placement in Crossfire affects temperature- again stupid me). Well, after installing it last night and finally running furkmark stress test to stress it, I got the dreaded red light on the new card and the system locked up at 100% gpu load. Shocked by this development, I did temperature logs and decided to run Borderlands again, after about 30 min of play, sure enough the system locked. It seems that once the GPU runs at 100% load for an extend amount of time, the PC would crash and I'd get a red light on the new card.
So from what I can see, I've got a few options
1) sell one of the 4850's and go back to single card.
2) sell both of them and upgrade
3) get a bigger power supply? (I believe the red light means that the card isn't getting adequate juice? I figure I would be in the clear with that though since I'm running a Zalman 600W that's pretty well rated)
4) Try something else?
Things I've learned
1) Crossfire is deceptively a pain
2) Temperature of the upper card will be higher than that of the lower card due to heat generation.
3) Crossfiring require more power than usual?
4) Buyer beware with open box items- you can only return them within x amount of days and there's no exchange for a new one or are they under manufacturer's warranty.
Anyways, it's days like these where I can empathize with those people that have completely spurned PC gaming in favor of the console.