I think you could use a nice fairway driver. Your Valkyrie is a speed nine, so why don't get a speed 7 or so?
I can definitely vouch for a 170ish Leopard. It is an awesome disc. I use it in star and champion plastic and you can shape all sort of lines with it. Get a dx one and see how you like it. You could also go the fancy route and get a Lat 64 river... It is supposed to be a little longer but yet just as controlable as a Leopard.
Anyway, from personmal experience, a Leopard will grow with you, it's an amazing disc.
bag: Beaver (putter) - Z,ESP,FLX Buzzz - Star,DX Glo Roc - Grizzly - Timberwolf - Star Leopard - FLX XL - X Nuke (the bomb) - Z nuke SS - Z nuke - Champion Boss - Star Katana