To answer your original question, JB -
I have the Sonnet box, and it's pretty fast...I'm pretty happy with its performance. I used it for the first time on the Audi shoot, and transcodes (in 4K HD) were about 1.5x real time. (This is my guesstimate - I don't have hard benchmarks - but they felt fast!)
If I understand what I have read about Sonnet v. Magma correctly, then Thunderbolt is a bottleneck which doesn't permit a level of throughput beyond what is possible with the x4 lane, so right now, the Magma v. Sonnet debate is a moot point, though down the road, when we have faster Thunderbolt, then the Magma is the speedier choice. There are no published comparisons between these boxes currently, so it is all a bit of theory and speculation.
I'm thinking about what to put in my second lane on the Sonnet chassis and am torn between an esata card, so I can use my old RAID and spending up a bit so that I can use SSD storage - not just for storage but the transfer speeds are truly unbelievable. I had an external 240gb SSD plugged into Thunderbolt for fast transfers on Audi - and it was a huge boost in being to get cards cleaned and back in the field, especially with those long event-driven takes. Sonnet has this SSD/PCi-e card which seems almost ideal:
http://www.sonnettech.com/product/tempossd.html - a pair of 240gb SSD cards and a Rocket, and you will have a souped-up transfer/transcode/storage station.
However, the jury on the use of Nvidia/CUDA accelerated cards, such as you would use to optimize Resolve or Premiere is still out: there is no clear answer to this question, as far as I can tell. One reduser posted that the Quadra 4000 card for Mac was working but provided no detail, so the report was unconfirmed, and other users chimed in to say that the power draw for these cards isn't there, on the chassis. These cards are not yet listed on the Sonnet compatability chart, so unless someone provides a clear report, we really don't know for sure. The best we have right now is conflicting reports.
YMMV, with the Magma box, though same rule on the power draw may be cautionary.
We could all use some more user confirmation on the use of CUDA cards in these boxes. Lots of speculation, few data points, right now.
It's kind of an expensive experiment, if you don't already own the card....
I'm also very interested in the Sonnet x mini server setup which you linked to - I already own a mini - but I would love to get a clear report from someone who has used this configuration in a DIT station application. The only issue with this solution is that once you buy the chassis, the mini, the display, the keyboard, and the mouse or touchpad, you might as well just buy the whole iMac. The only reason I'm thinking about the mini chassis is because I already own the mini, display, keyboard, and mouse....
I'm currently running a 27'' iMac as my DIT station, with the Sonnet box and Rocket card. It's not super portable or totally great in the field, like the mac mini - but it is self-contained with a 2k screen, which is really nice for viewing and playback. With the Sonnet box, it is faster than my old tower, for sure.
The big shortcoming on both the mini and the iMac solutions seem to be CUDA acceleration right now. If we can find a way to make that happen - if anyone has any ideas - I wouldn't care if Mac ever released another tower again - the new computers are fast, and Thunderbolt adds a superb degree of flexibility and expansion (even though it is NOT CHEAP right now!!)
anyway - I hope this helps. I am definitely moving everything, as fast as I can afford it, to Thunderbolt and SSD...in the coming era of Dragon, there will be no such thing as too much speed or storage....