I have no idea if that brocks exhaust is any good, but the price is crazy low. They sold for 999.00, originally. I believe it's made by Hindle? 300 wont even buy a chinese made system. If you search "Brocks z1000" he got some good numbers out of that system.
The reason so many went with the Akra system was because if Ivan's flash. His flash was built with the Akra full system in mind, so you get the best gains with that system and his flash, together. You have that flash, right? It's worth far more than an exhaust to overall performance.
Overall, I'm not sure how expensive the akra really is. Obviously, it sells for a lot of money, but if you look at ebay, used ones still sell for 900.00.