I love my 870's and have gotten years of good, heavy use from my 20 ga, moreso since I finally got rid of the one Mossberg 500 I had.
However, I don't know what
the heck kind of 'gun' that one linked to on Flickr is ...
The only customizing I've done to my 20 ga. 870 after 25 years of use is to get it set up for choke tubes. And now it's perfect.
This pretty much sums it up:
Best advice I can give is to obtain a US made pump like an 870 or 500 and shoot the bejabbers out of it.