There's plenty of debate on 9R vs. Boost vs. aftermarket turbo. I don't have a turbo (on a sled; I've got two turbo-diesels and a Porsche 924 turbo), but the biggest piece of advice I'd give if you're considering aftermarket is to talk to people who are or have run an aftermarket turbo. Everyone "has a buddy who could never get his XYZ turbo kit to work right." There are people who are happy with aftermarket turbos, but some of them switched to a Boost. Also, power will always make a sled more rowdy, and a turbo will always have more than NA (maybe less worth it the lower you ride though). That said, I think you're spending money in the right place if you go to an aggressive 155" track. If the snow where you're at is like mine, you're just going to tear stuff up if you take it out in the next couple weeks. If you feel like changing something around instead of sitting around waiting, why not?
Incidentally, what you've currently got is the direction I'd like to go on my next sled. I've heard good things about SLP's twins, but the initial tune at least wasn't that good. You might want to reach out to
@TRS on that: he's done some tuning, plus he'd be able to help if your clutching could use some attention. You might make as big a jump on what you've got as you'd (hopefully) get in a big bore, but for hundreds and not thousands of dollars. Obviously, a big bore twin-pipe would be the ultimate NA - assuming it was tuned right. If I had money to burn, Dan's stroker and twin pipes sounds pretty spicy. Finally, you'd asked about using your current twin pipes with a conversion. It'd probably work, but SLP does make pipes specific to the 9R, so I doubt it'd be ideal. But it's worth asking SLP, if you do go that direction; I guarantee they know how a 9R runs with 850 twin pipes.