I've been racing 10k's and up in my Katana IIIs and I want to get a new pair of racing shoes and use my katanas for long intervals/tempo runs (until they wear out). I have a pair of marathoners but i don't really like them. i have a pair of streak xc IIs but my feet and legs feel beat up wearing them over 10 miles. any suggestions? not limited to nike, that's just the shoes i happen to have at the moment.