hi roger- i'm not a mac user, but i concur.
i'm surprised that the feedback hasn't been a problem.
there's some really good, (relatively) inexpensive
mics on the market. rather than go w/ a vocal mic,
like the industry standard shure sm-57 & 58,
i'd look at either a behringer "B" series or one of the
russian oktavia condenser mics. both are under $100,
available at the guitar center ect.
behringer also makes some decent small mixers.
for your use, 1 or 2 inputs w/ 48v phantom power is all
you'll need.
garageband has some fantastic features for the $$,
you can't go wrong w/ it. the trade mags have been
gushing over it for months.
you may be able to find some help/ back articles at
www.keyboardmag.com.
k