First thing. If you want to run the S1X with 1.7 rockers it's gonna cost 2-300 more than if you just got a little bit bigger cam. You'll lose a little bit of fuel effeciency and the idle will be a little bit rougher with the bigger cam but it'll be a bit cheaper.
S1X with 1.6 rockers is .514"/.526" With 1.7 rockers it's .545"/.559" where as the stage 3 intense cam is .541"/.554" It's just a TAD bit smaller BUT you won't have to buy new rockers. You can reuse the stock rockers(assuming you still have them since your sig says you have 1.9's)
Second thing. If you're already ready to spend the 1800 bucks on stage 3 heads, why not just fork over the extra 200 and get the stage 4 done. You're already gonna be spending 1800 bucks, you might as well get them the best you can and spend the extra little bit. Look at it this way. Save the 200 bucks by getting the stage 3 cam instead of the stage 1 and 1.7's and put that 200 towards the heads. You're still not really spending anymore than what you wouldve to begin with and your getting better flowing heads with an EVER SO slightly smaller cam, probably unnoticeably smaller.
If I was you..seeming like you have a pretty nice budget I would get the Stage 3 cam(which intense says is streetable), the stage 4 heads since you'd save the 200 or so from the rockers, 130# springs. Not sure if you would need a double roller...i would assume so. And i'm sure you'll need a few other odds and ends too.
EDIT: I could've swore I read stage 3 heads and not stage 2....well then. That's a big diff in price so now if I was you i'd do it like this lol
Stage 2 heads...good for .600 lift so you'd be fine with a stage 2 or 3 cam.
You could still do the stage 3 cam but I think I would do the stage 2 and run crow 105's since you can probably use an OE chain and a new dampener...I don't know for sure though..MAKE SURE FIRST. I'm betting you would need a double roller for the stage 3 cam since you'd probably need 130# springs and to do that properly ive heard is a decent bit of work....so like I said i'd stick with the stage 2 cam
Sound ok? I dunno, you tell me.
