Dual CPU's are NOT 50% faster than a single CPU!!! See Tweakers Page - Deciding between a single CPU or dual CPU's
There are many cases with 6 bays, heck, you could get cases with 26 bays if you want.
6 Bays is sufficient for 18 SSD's or 10 conventional HDD's, so I would not worry about that.
The E5-2670 is ill-advised. It is way too costly and far too slow, even in dual setup.
Internal parity raid can only be done with a dedicated raid controller if you like decent speed.
Have a look at New System Build for some ideas.
as the chart cc_merchant points out, due to problems with adobe's software, there are times when premiere wont properly use high cpu core counts. it also shows the limitation above 32/64 with dual xeon's. the problem is even worse for photoshop than premiere. adobe also doesn't support gpu encode/decode like intel quick sync, which in h.264 4k projects would let a 4-core i7 outperform a dual xeon or i7-E.
to overcome these software limitations, an overclocked i7-E is often recommended, as it has less cores running at higher clock speeds. the overclocked I7 system will require you to build it or buy from specialty shop, this may also let you get a case to fit your needs. the E5-2670 v3 cpu is a very powerful cpu, but with its higher core count can be crippled in some situations with adobe's software. there are xeon's that match layout of the i7's with lower core counts at higher clock speeds, like the E5-2667 v3. but these are even more expensive than comparable xeon's and cannot be overclocked to match the higher clock speeds of the i7's.
if you can wait till you need a machine to handle 4k in about six months, the new i7 broadwell-E & xeon broadwell-EP cpu's will be coming out soon and perhaps even nvidia's new pascal gpu's. the 10-core i7-6950X should make dual xeon even less attractive and the 8-core i7-6900K should become the next go-to system for most. intel will also be close to releasing its new ssd's, which will be several times faster than the already insanely fast m.2/pcie ssd's now. that should help push down the prices of ssd storage at all tiers. the faster ddr4 memory in the i7 builds also helps with performance. if you do buy a system now, make sure its using ddr4 2133 or higher. the hp z420 and z620 seem to be using the older v2 xeons with ddr3.
I get it and the charts tell the picture. I am going to wait and have my friend build a system from scratch. The z420 are out their refurbed for next to nothing so I may just get one for temporary use doing 1080P.
Another quick question. Getting a refurbed z420 just to get by and they are available with different processors. I was looking at the E-2670 2.6 eight core but I see 2 models with a E-1620 3.6 four core and an E-1650 3.2 six core.
The six core and the eight core are almost the same on CPU benchmark. Six core better because of faster clock speed?
Thanks for the education.
total speed of a cpu is # of cores x clock speed, including turbo frequency. that's only a rough estimate for comparison, and different version/generation chips from intel will be faster or slower at the same clock speed. so its possible for different core counts to be similar in performance, and an overclocked i7 8 core faster than 12 core xeon.