MagnaFlows X Pipe System

I started a discussion in the Tech section about this where as so far Ive had no replies.
Im interested in adding Patriot Ceramic Headers and Dual Exhaust to my otherwise stock L48 / 1977 / C3. I believe when I had the engine rebuilt in 1995 that he stated that he bored the cylinders closer to 9:0 to 1 and installed larger pistons.
As I was looking at a Mid America catalog I came upon a X - pipe system for C3's that was advertised as being "new".
I had heard rumors of HP boost;but wanted to know if anyone had installed such a system or could swear by the added benefit, compared to running exhaust pipes straight back as 1974 or before?
After several days of no response, I decided to check out MagnaFlows website to see if I can learn more.
It seems they claim that the X-pipe crossover itself balances the exhaust better from all cylinders compared to dividing the exhaust output in half with duals only.
Besides this, they claim it aids in quietning the exhaust.
Im sure they are all about tooting thier own horn, but I wanted unbias consumer input.
My local shop says;" dont expect much noticable HP boost with headers and duals" However more others, claim otherwise!
MagnaFlows sells just the X crossover piece so a person doesnt have to buy the kit that Mid America is selling.
My headers are coming from Corvette Central, the mufflers from Ecklers, and a local muffler shop is bending 2 1/2" pipe.
Should I add the X crossover member or save my money ?