Wait... you have a 290 already and you want to buy lower grade cards? I fail to see the logic here.
You should start a new thread in the Build a PC category and explain your situation there... there is not enough information to know anything right now. Someone might be able to help better with that info.
No im going to be building a pc and i had an fx 6300 and an r9 290 picked out but now i found two r9 270's for $200 with a crossfire bridge and was wondering if they would be worth it instead of getting a single r9 270. Then i was considering buying both cards and selling them to make a little extra.
Ehh, here's what I'm going to say.
With the FX-6300, an R9 270 will be enough as long as you don't play the AAAAAAAAAAA++++ titles. It will push games like BF4 and Farcry w/e to around medium settings at around 60 FPS or more (1080p). The 290 will do the same at either higher framerate or higher settings. If you like eye candy, a 290 is good, if you like money the 270 might be better. Both cards will play games at 60 FPS, one can just push more pixels than the other.
Well i have talked to a friend of mine and detirmined that im getting the 8 core fx series cpu and the dual 270's. I appreciate all of the help guys
i would personaly recommend a locked i5 on a cheap H97 mobo + R9-290.
If you can afford.
Locked i5 will have no issues maxing out a 290 in most games..
Because it has way better per core performance then an FX cpu.
Well my budget is only around $500-600. 600 is about the highest.
ah okay, yeah then an i5 isnt going to fit.
However i dont think that a FX8 core + decent cooler, + decent mobo will fit either to be honnest.
But i dont realy understand you initial postings, you allready have a 290 and a FX6300?
or dont you have anything yet?
It all fits however i dint have any of the parts yet
I would opt for the best single card you can buy. If you have goals beyond that, double up if it's a tangible thing. In other words, don't crossfire or sli unless you are after a performance level that surpasses the best single offering. Doubling up on mid grade is just poor planning. That's my 2 cents k.
i can confirm that the 8 core plus 2x 780tis and a C: boot ssd will bottleneck
so we swapped the build to the 3570k and all was well
actualy if i recal, that build was before we had the sli 780s
so even dual 7970's were bottlenecking 
dont know if it was just some strange combo of the hardware or what,
but when we swapped the mobo and cpu for similarly priced intel stuff at the time, everything magically was better
Well i will still get pretty good results with a single 270, and i could just add in the crossfire later on. Also i vould just sell the cards in the near future.