Well now I feel like a dummy. I saw E7-8870s in the list before and thought it would be more of a boost than just double the accessible RAM which won't do us any good.

8870s can address 4.1TB while the lowly 4870 can only address 2.05TB I don't think that will give us the kind of performance boost we are looking for. I guess next time I'll make sure to check the specs instead of just going... Ooooh bigger numbers, has to be faster right?

Found 4 8837s for 35 shipped, they are on the way... LOL
Cache is the most important factor here, mining cryptonight with xmr-stak. The configuration of the miner should be based on the amount of cpu cahce available. Each miner thread needs 2Mb of L3 cpu cache.
For the E7 family i made this formula to estimate cryptonight performance:
13 * corespeed in ghz * (amount of cache per cpu 2 ) * number of physical cpu's * = Totalt H/s running one thread per 2MB cache
For me:
13 * 2,66 * (24/2) * 4 ~ 1650 H/s