Question Should I test and then Overclock each Graphics card individually before Crossfire-ing them?

[Marquesis]

Sys Specs :
-Gigabyte GA-990FXA-UD5 R5
-AMD FX-8120 -3600 MHz -8 Core
-(Asus) AMD Radeon HD 6670 (x2)
1 GB GDDR5 - Crossfire
-(Crucial Tech) 8 GB (x2) DDR3 Ram
-PSU - 1100 Watt
Now, I know before you say it (buy new) but not the best time for me to do that so going next best route. I've already upgraded my graphics cards Bios but the next step I'd like your feedback on . I hear different opinions about instabilities concerning the overclocking of two cards Crossfired/SLI compared to just OC one card.
With that said, hence my question: Should I test each card individually to get each ones capability, then pick a middle mark that both cards could handle, then OC both and then crossfire them? Or crossfire first them, then test, and then OC ?
I appreciate all feedback and thank you for your time spent helping me .

 

[Barty1884]

IMO, there's no point in checking them out individually, as it's only what they can do in CFx that matters at the end of the day.
You have the added issue of cooling/airflow once you have two cards in CFx .... what it could do with ideal airflow is one thing, but once you cut down on that airflow, it might be a totally different animal.

Boot with them each individually, ensure they're both working - but beyond that, get them in CFx and see what they can do.

 

[Gam3r01]

Agreed, make sure each card works on its own (stress test), but any OCing should be done with both installed.