I agree. Alot of coin for that.

If you plan on doing any other work to the engine I would seriously consider true header exhaust.
Be very carefull of aluminum exhaust.
If you overheat the engine due to lack of water flow the aluminum exhaust can melt down.
The headers ( steel ) will usually survive this.

Dana marine manifolds!

I have EMI exhaust and I am very satisfied. Expect 1 or 2 MPH gain. This is the best place to start with the upgrades. You get rid of the wet riser joint and improve reliability. Any engine mods you do, especially the Cam would need them anyway. It is better if you ditch the silent choice, if you want to reduce the noise use mufflers to compensate.
Good luck!

I agree with Griff. 1-2 MPH gain at the most.

I replaced my heavy azz stock exhaust last yr with SM. Lost a good 80# between both motor change overs, but seen zero speed gains. Motors have a different sound now. More of a tingy sound now than the deep tone the cast steel gave it.

My previous boat had a blower motor with straight thur hull Merc/Gill exhaust. I got tired of the fulltime loudness real quick. Installed silent choice, had no speed loss.