Question is what will you benefit more from? Lots of slow(er) cores or fewer faster cores? If you're in charge for the build you should investigate and provide this data to your boss if possible so that he can see that this makes sense.
Again, I don't know what software you're going to use exactly but I don't see how will a Quadro / FirePro card can assist with data crunching? I believe it's only for CAD applications and stuff like that.. If you don't know the answer then you should definitely check that out as getting a mid / low range Radeon 6xxx / 7xxx series will save some money that can be used for more processing power, and almost all of these cards can support up to 6 displays.
If you were assigned to come up with a build you should really investigate, as it's your responsibility if these machines perform below expectation and your reputation on the line.
The questions I would ask myself are:
- Cores vs. speed.
- Queue depth required. If it's high, you may actually need a large SSD. If not (and by your description I believe it's not), maybe Hard disks will be sufficient.
- Is this work sensitive to HDD speed? If so, will it require a boatload of storage area (then you might want to get HDDs and raid them, and maybe a small SSD) or will it fit into smaller storage (then consider a large(r) SSD). In case it's not sensitive to HDD speed, a small SSD might be sufficient.
- SAS vs. SATA . Maybe SAS drives are more reliable, operate faster (15k does seem like they're much faster),maybe they have certain features that normal SATA drive don't (look at Intel for example, their SB-E line consists of processors that are 6-8 cores and are almost identical to the Xeon line at a lower cost, but lack certain features such as ECC memory support to prevent servers from getting those).
- Graphics card required. Do you need a workstation graphics? If you do, (maybe for the Adobe CS or w/e), how important is it? Meaning, how much work will it do? Once a week? Once a day? All day long? If it's only for Adobe CS and it's rarely used, maybe you can get an entry-level card such as the FirePro V3900 (review -
http://www.tomshardware.com/reviews/firepro-v3900-revie...). Then again, I believe that Adobe CS is currently optimized for Quadro, and it's up to you to find out.
There are a ton more questions you should ask yourself and a whole lot of data you should gather. My suggestion is that you do some homework (if you haven't done so already) and also present all the data and maybe some actual benchmarks to your boss so that he can understand the reason behind every decision you've made and as an added bonus he'll see that you're taking your job really seriously.
P.S. That's the kind of work I do when people ask me to make a build for some special tasks, so I believe you MUST do it as well to avoid making some really bad decisions.