Well let me ask you a few questions.
1. Do you use one monitor if so!
a. It is horribly overkill to get more then one graphic card.
b. SLi/CF scaling has improved over time but there is no need for multiple cards
b2. People often times run into issues with stuttering or what people call a non-smooth experience with there cards in SLi/CF.
2. Based on the performance that your 7870 was able to dish out if you were to go Nvidia I would go with the 660Ti it competes against the 7950.
http://techreport.com/review/23981/radeon-hd-7950-vs-geforce-gtx-660-ti-revisited/4
a. if you want the best long term value the 670 is the way to go. However not everyone can put a 300-400 dollar card.
(prices of both cards from top to bottom)
http://pcpartpicker.com/parts/video-card/#c=113,101&r=2048&sort=a5
3. Also with all this out there and suggestions from left and right what does your system comprise of.
CPU:
MOTHERBOARD:
RAM:
VIDEO CARD: WIP (work in progress)
POWER SUPPLY:
CASE: (Helpful in advising a card that would best suite your needs on cooling)
If you have a store bought computer please provide the following.
COMPANY NAME:
MODEL NUMBER: