I agree, in part, to what Chris has said above. On standard headers, and with a standard engine aftermarket cans are all pretty much of a muchness. Especially if you get a Power Commander and custom map done. Yes the Akra cans might make a bit of a difference (for instance they often have tapered link pipes and tapered internal cores)...but you are probably chasing the last 1 BHP out of a tuned engine. A decent custom map and a skilled dyno operator will make a bigger difference IMHO.
With regards to the SP1/2s, the standard end cans weigh an absolute ton. They are huge, heavy lumps and are very very restrictive. Buy the can you want, junk the standard ones, stick a PC on, do the flapper mod and get a custom map done. That'll transform the bike, believe me. Proof of the pudding? Before and after power traces.....8 extra gee-gees at the top end and a big hole smoothed out in the mid-range (this was with the MTC cans). That's what a custom map can do. Both traces were with the same set-up....the only difference was the tweaking on the Power Commander. I shudder to think what power it would have made on the standard cans (110BHP at the most I reckon).
A pair of titanium
MTC slip-ons would be £400. A pair of
Akra slip-ons is £1053. Thats 600 nicker difference. £600 would buy a Power Commander and a custom map and still leave £250-£300 in your back pocket. OK, the Akras will have a bit more "street cred" and might make a couple of extra BHP, but for me, £600 buys me 4 trackdays. Personally I know what I would be doing!!
Want to actually ride the bloody thing first before I fit anything...it's only been up the drive and straight into the garage 
Lurvley bikes.
