I think the 7970's are the best bang for the buck as you can find decent ones on ebay for about $300-320 but make sure they are not beaten up by other miners.
7990's can be an option too at 1200Mhash/s but as far as I know only PowerColor makes them and they are hard to find and they seem to occupy more than two PCI-E slots and there are other issues too. like price.
A test bench is fine. I keep my cards in a non crossfire setup, since they won't benefit from it for mining purposes.
Best of luck.
Thanks for the info, running searches for the 7990!
Incase you would like to mine litecoin, novacoin, bbqcoin or other scrypt based coin you will need more than that 4GB of RAM when using 4 GPUs.
You will also need powered risers for +3 cards so you don't burn your 24pin mobo connector with too much current through 12v lines.
With those risers comes the necessity to hang those cards from something since you can't directly plug them in to your mobo.
Club3d makes 7990 too, atleast in europe you seems to be able to get an 7990 for the price of 2x7970s. Since 7990 are supposed to be binned chips you may end up with better chips and thus lower power consumption or better overclocking. If you want to save those PCI-E slot on your mobo then 7990s might be something to consider as it's actually 2x7970s on one board. They do need 3x8pin PCI-E power thoug. With 1200W PSU you can probably run 5x7970s or 2x7990+1x7970 with some underclocking.
Building a rig now means mostly that you trust on scrypt or on the continous and rapid hike in bitcoin price. Those ASICs will start to skyrocket the BTC difficulty shortly and that might make SHA256 GPU mining unprofitable during the summer.
You will also need powered risers for +3 cards so you don't burn your 24pin mobo connector with too much current through 12v lines.
With those risers comes the necessity to hang those cards from something since you can't directly plug them in to your mobo.
Club3d makes 7990 too, atleast in europe you seems to be able to get an 7990 for the price of 2x7970s. Since 7990 are supposed to be binned chips you may end up with better chips and thus lower power consumption or better overclocking. If you want to save those PCI-E slot on your mobo then 7990s might be something to consider as it's actually 2x7970s on one board. They do need 3x8pin PCI-E power thoug. With 1200W PSU you can probably run 5x7970s or 2x7990+1x7970 with some underclocking.
Building a rig now means mostly that you trust on scrypt or on the continous and rapid hike in bitcoin price. Those ASICs will start to skyrocket the BTC difficulty shortly and that might make SHA256 GPU mining unprofitable during the summer.
Thanks for the post!
After reading both of your posts I am searching for the 7990s! Since they are a compilation of two 7970 on one board I'd think that would solve the PCI issues. If the ASICs arrive and do what they are supposed to then I am definitely going to mining LiteCoin but since RAM is comparatively cheap that should not be an issue. If Butterfly Labs follows through on their current promises and such and the ASICs make the splash there hypothesized to, then I can see a few of those little $149 units in cluster for the future. Again its more about support of the currency than profit so with a couple of those on pool and the rig I'm planning running solo for LTC, there should be some fun ahead.
Mmmm so you're looking into an $800+ GPU, but when it comes to ASIC, you choose a $149 ASIC that delivers 4.5 Ghash, instead of the $1299 ASIC that delves 60GHash?
That doesn't sound right to me considering that with 10 jalapenos you were 45Ghash for $1500 when you get 60Ghash with one Single for $1299