As a bass and guitar player - both secular and church - I would advise against single driver buds of any kind - tho' I realize most are budget constrained. Been there, done that and paid the price (many times over). For bass you REALLY need multiple drivers to get the sound stage and separation so it doesn't all turn to mush. The SE215's are fine for entry level, but you'll soon realize they have limitations that all single drivers do.
Think of it as your home stereo system only having one speaker and everything being pumped thru it.. the speaker is not physically handle it well and it can get very mushy - hardly CD quality. Now put that in your ears.. you get the picture! Still better than a wedge tho' IME.
Yes, I get there's a budget and most head down the single driver path, but over the last 5 yrs I have run the gamut of universals vs customs, single vs multiple driver, wired vs wireless and that includes UM1's, SE215 and now 1964 Quads (for buds), Carvin EM900, PSM200, and Senn G3 (wireless) and Aviom and P16 systems. I currently run Senn G3 with 1964 quads with band (X32 console, mixing my own IEM's from my iPad) and Avioms at church. Very happy. Stupid silly bass if I need it. GeriO will vouch for that!! FWIW - I only ever used the 215's that came with the PSM, never tried the 4i (?) that came with the Senn's and the Carvin buds only once.
Do some research - there are some REALLY good and [relatively] inexpensive multi-driver buds out there, both custom and universal fit. GeriO (and others) recommend the UM30's.
However, none of the decent ones are cheap. I've seen too many folks dump IEM's and go back to other monitoring tools (wedges) because they could not find themselves in a single-driver delivered mix.
The best advice I can offer is DO NOT GO CHEAP on buds..
Good luck..