Those won't be enough, unless you are crunching on low-power computers.
I've recently had some bad experience with my ARM systems - the BOINC client works, but there is no workload for ARM platform (no longer supported).
NUCs are still an option, but I'm not sure about performance yet. If you are planning on running a huge server on that thing - you might run into some trouble.
According to the data, provided on the product page, the battery pack is capable of running a 65W laptop for 22 hours, which adds up to 1.44kWh (assuming that they tested it not with the actual laptop,but with a continuous 65W load).
When we go over battery spec, we get a bit of inconsistency: 12V pack with 100Ah capacity gives only 1.2kWh... So, we can go with that number as our baseline. I'm not sure if these numbers are given for a single battery pack, or the whole system, so let's be optimistic and count it as one.
Now, let's talk about efficiency and charging. Here is another optimistic chart, which displays a relation between Solar Panel efficiency and how fast does it charge the battery:
This thing is actually a lot more complicated, because it involves variance with weather, sun height at the time of year etc, but on a good day you get a peak efficiency of 65% with a daily average less than 40%.
This only gives you an average charge rate of ~50W, which on an assumed 12-hour day makes up only 600Wh total charge, or 1/3 of a single battery.
That, of course, only applies if our cruncher does not work during the day. If we evenly split the resulting charge for 24-hour cycle, you will only have 25W to spare, which is an equivalent of two Atom-powered NUCs, or this:
http://www.phoronix.com/scan.php?page=article&item=phoronix_effimass_cluster&num=1
So, with two cells and two battery packs you can run a 50W continuous load 24-hours a day. Not too much to justify the expense.
To be honest, that battery size is an overkill for that PV system, I think it was designed to be a nice battery-powered backup with a small assist from solar energy, rather than an independent unit for off-grid living.
It has a pretty decent inverter, which will allow you to run your Xeon farm for 1 hour, but that's it - you'll have to go back to the electric outlet....