Harsher engagement clutches will be more likely to damage an unprepared transmission. That's about all I have to say about that. These trannys have seen up above 300hp, with little to no modifications, but I wouldn't bank on it, for sure.
About the price, $300 is good, actually. It usually ranges from there to 450, from my experience for a clutch install. A flywheel isn't going to cost ANY more to install at the same time, since they have to remove, surface, and reinstall the stock flywheel anyway, so if you forgo that option, it may cost you less, sans the price of the flywheel itself, of course.