The Akra system is ridiculous because it has the Ducati tax. It is the way to go if you're anal about preserving as much of the warranty as humanly possible and/or are a fan of the looks, but otherwise it is extremely overpriced. The official tune it comes with is lackluster as well, aftermarket tunes routinely outperform it. My Ducati tech told me the warranty is not an all-or-nothing deal, as in if you change the exhaust it only voids warranty for the exhaust. You could have brake system failure and it would still be covered. If the engine blows, it would only not be covered by warranty if they could prove the exhaust caused the failure, such as making it run too lean. However, it seems every dealership is different in how much they are willing to "fight" for you. I've heard of guys taking their bikes in for stuff that is easily warranty related, but the dealer was resistant to putting in the claim because it's more of a hassle than just making the customer pay for it. Sometimes the convienence of not having to deal with stuff like that is worth the ridiculous costs of things like the Akra and "official" Ducati performance "upgrades."
Also, if you're just going for looks then get whatever cheapie exhaust fits your fancy. However, most of these less expensive exhaust options have little to no development as far as the performance side of things. They're just bending tubes trying to make it look cool and hopefully keeping each header the same length. I wouldn't be surprised if on a lot of these cheap systems, there's more/less resistance on the front/back headers causing performance losses. Removing the ridiculous emissions control stock exhaust and throwing more fuel in a tune will always net more power even if your exhaust is designed like shit. Dynos are all different too, so anyone can throw a bike on a dyno and make a cool video showing how badass the system is. I would be nervous throwing a random system from one of these cheap producers on my 20k+ bike because it could lead to problems sooner than I'd like. Very expensive problems, negating the money you saved on going with a cheap system.
That's why I think it's a better choice to go with the less expensive options from established manufacturers like FM Project, SC Project, Arrow, and so forth. They have racing pedigree so you know the system they designed is optimized for performance and engine health. They didn't just sit down and say, "let's bend some tubes to make it look as cool as possible and call it a day." I strongly recommend spending a little more money and preserving your investment over buying a cheapie and blowing your motor pulling on the back straight at the track well before something like that should ever happen.