Yo Andrew C! I have had some call to mic cellos. Are you still doing the SM7? It is a very good vocal mic for some folks, and even after you find a better studio mic for the cello, the SM7 will remain a good *live* mic for the cello. In the studio, I have had my best luck with small diaphragm mics backed off a bit to decrease bow scratch, but you need a good-sounding room for that (quiet).
On the more affordable end, I've gotten fair results with Oktava MK 319, Studio Projects C-4, AKG C2000B, and AT4033. The two latter are both small diaphragm mics, but in larger housings, and tend to work on vocals better than pencil mics. For some singers, you need 2 pop filters with SD mics. Lately, I use a pair of KM184's, a B.L.U.E. Kiwi and/or a C414. Not because they are "great" mics, but they are what I have. And- I have no complaints. The KM 184 is underated by the mic geeks. It has worked very well for my needs Good luck with whatever mic you settle on.-Richie