seems i find myself saying this a lot frequently--i'm with rimshot here.
i don't currently own any SM57s, but i've used plenty of them in the past and i do own three of the 545's, which were the sm57's predecessor. i find the 545's to be a little ballsier (grittier) than the sm57s i've used in the past and i like the 545's a little better on rock guitar amps, snare and toms.
i've also got a pair of the senn 835's, and i like them a WHOLE lot better than my pair of sm58's. as rimshot said, they're a little more peaky higher up, so they seem a little more aggressive on some vocalists. on some vocalists i like the 58s better, but i'm not one of them.
i also like the 835s on rock amps, toms and snare, depending on the sound of the amp, toms and and snare.
they're really very different mics with similar characteristics, and while i understand your desire to "be consistent" with your mics for your toms, please understand that different sized toms sometimes benefit from different mics. it's not about being consistent--it's about matching the sound up with the right mic for the job. when i fully mic my kit, i generally use my 545's on the lower toms and the 835s on the hihat and upper toms. my kit's expanded a bit since the last time i mic'd it all up, so i'm gonna have to experiment again.
but anyway, i'd recommend getting a pair of each if you're looking at getting 4 mics. but then again, i'd rather have versatility over consistency.
wade