Looks good. Not a lot of rocket science here in straight pipes and resonators. The biggest debate is in the "x" section.
I prefer the gentle curve with a kiss in the middle to allow the two separate paths to balance pressure while losing a minimal amount of the total area of the two pipes. Others want a sharp angled "x." Others want to force one exhaust path through the other in the "x," effectively merging the two paths briefly into one in a space that is the area of just one pipe.
I have looked at a bunch of x pipes for a variety of cars from a variety of manufacturers, and the design of the "x" varies. I am not an engineer so I am not sure what is actually best for flow.
Price is always the determining factor. Decent resonators are $50-$75 each and a resonator-less x-pipe can be bought for about $500. Add the expense of 8 welds. Total cost $825-1000. The cheapest quad resonated x-pipe currently available is the Borla 60506 for $1261. http://www.summitracing.com/parts/bor-60506