I have worked on Corollas in the past and wiring a deck, amp and power wires was a B*#@^ I guess only because the interior pieces were put together much better than my 15 year old Honda...
That being said I was able to fit a Pioneer AVIC-N2 in the DIN opening with a little bit of fitness. The install took longer than I originally expected, but overall not that difficult.
It may not be what you want, but I think fabricating a 7 inch touchscreen in the area would look much better, but again it is a matter of opinion and budget I guess.
As for the amp you reference, I have never seen something so small. You definitely will not get 500W out of that thing. However it may be a cheap and small solution to power your factory speakers off of your carputer.