I"m going to toss in a vote for a Leopard. Because of the distances you're getting now, and because you said you're flipping some of those (and the Shark gets wonky), it's clear that improving your form is what you need to do if you want to gain distance. Valk is an excellent disc, and that or a Sidewinder might be the best right now for your distance driver, but they're probably going to match your Katana at the moment, so if you can control your Katana decently you may as well keep using that.
That said, pick up a Leopard in good plastic. Use that and your Squall for a bit. Both of those will get you out to 300' with just a little work, and both can go farther eventually. The Leopard is going to teach you more about your form because if you start turning it without intending to (at your current power level), you'll know that you've got some heavy OAT going on. When you can hyzer flip your Leopard, then you're ready to step up to some faster discs and you'll definitely be seeing a lot more distance (from all discs).
Another option might be the TL, but I'm thinking the Leopard and Squall will get you on the road to improvement faster, and they're both capable of longer distances than you're currently reaching with those much faster drivers. A few years back, I was in almost this same exact situation - same distances and same discs! lol.