Yesterday at the rehearsal room I checked out my new Roland Cube Street EX with the Kemper, so I want to share my experience... here is a short review.
The sound is well balanced and at "maximum power mode" it can be really loud! The volume should be enough even for using it as a personal monitor on stage with a loud metal band. Compared to the bigger and more powerful active speakers as e.g. Yamaha DXR10 it is not so fat at the low-end, of course, but IMHO still enough.
A nice "side effect" of the Cube Street EX is, that it it can be used with 8 AA batteries... great for playing outdoors, street music or just for connecting an mp3-player at the camping ground. Optionally two of these devices can be combined to a portable stereo PA.
The included amp simulation sounds quite good, not "digital", but "organic" 
. There are 4 presets with fixed gain settings: clean, crunch, lead and an acoustic guitar simulation.
The quality of the included effects is nice, the options are simple, but sufficient: one control combined for chorus or delay (not both at the same time possible) and another control for reverb.
I guess the amp simulation and effects processing technology is similar to the one used in the Boss GT-100 or GT-1.
Conclusion: the Roland Cube Street EX is a great all-in-one device, some kind of "panacea" and can be useful in many situations, also as a stage monitor for the Kemper. It's not too big (about 50 x 35 x 30cm) and light-weight (about 7,5 kg).
It's worth to give it a try! The price is about 550 Euro.
Note: Roland offers a quite expensive transport bag (about 70 Euro). IMHO this is too much for such a simple bag... the Cajon bag by "Fame" (Music Store Cologne, Germany) fits as well and the price is just 15 Euro.
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