In my opinion its kind of a different animal. If you want to build a DIY subwoofer that is like a typical active home subwoofer, than that O Audio Bash amp makes sense. It's all integrated, you just plug it into a receiver like normal.
A prosound amp and processor, is two extra pieces of equipment to find space for, and are especially ugly. It works great for people like me that have racks and no wife, but if it comes down to being in someones living room on a equipment shelf, its a judgement call. The upside is with a processor and convection cooled amp, your getting a lot more configuration, probably much better speaker protection (peak limitors, etc.), plus without having to conduction cool you can gets gobs of power for cheap.