I am currently running a Gigabyte 6870 OC and I'm wondering if I should purchase another card for around $100 as a temporary fix to run higher graphics settings for my 1920x1080 monitor or should I just wait out till around next year and purchase a higher end card?
Also if I do go Crossfire with my 6870, how long should I expect before I'd have to upgrade again?
My personal recommendation would be to wait, as crossfire and sli are both inefficient over a single card solution.
i'd say wait and save up another $150, by that time you will likely be able to afford a 280x or gtx 770 which are both MUCH faster than the 6870
I've thought about buying another 6950 for my computer build since the R9-280X and 290/290X are both outrageous in price, but there's really no point since I'd be limited by the 1GB of vRAM which also be the case for you.
I'd really recommend not wasting your money, just wait until you can afford a GCN or maxwell card.