welcome

one mic for the whole band ?

mmmm

Calrec Sound Field
:)

just kidding ... very expensive

one mic will take quite a bit of experimenting
... the best mic will probably turn out to be one of the condensers
but as to whether it will be a large or small diaphram is hard to tell
the room is the big factor

15 x 15
is that feet ... or metres ?
I can't see where you are from so I can't make a guess
how reverberant and does the wall and ceiling have absorbtion

kick mic
look for an ATM25 second hand

the room is 15x15 feet. has excellent acoustics, fully absorbed with sound proofing

What I would do is record the band with a stereo pair in [="http://en.wikipedia.org/wiki/ORTF_stereo_technique"]ORTF[/]="http://en.wikipedia…"]ORTF[/] configuration. Try it with your pair of 57's. Experiment with position of the instruments and the mic pair. This is very easy to do and will give a good audio picture of the band. Play as quietly as you can while maintaining your groove and energy level.

If you like the technique, you can get a pair of small diaphragm condensers. These will be good for drum overheads if you ever move on to multitrack recording. I like the Rode NT55 as a starter SDC, but there are better mics for more money.

There is a post on kick drum mic samples [[url=http://="http://www.recordin…"]here[/]="http://www.recordin…"]here[/].

Try placing your omni mic on the floor in front of the drum kit.