Monitors will depend on what you want to hear. If it's just vocals ... I'd suggest the Core systems (hot spot) powered monitor. It packs 85watts into a small, stand mounted box about the size of a lunch box. It can also power two more regular hoy spots, so that boosts it up to 144 watts into 3 separate speakers.
For more intense material (bas, drums, etc) you'll need something bigger. The new JBL eon10's are pretty handy - already powered, wedge shaped and sound great.
Monitors should be carefully thought out - they are a VITAL instrument in mantaining your hearing, anbd protecting the audience from too much volume as well.
If you have the mains high up on sticks BEHIND the band, and all you need is a little vocal "in your face" then get the hot spots - all three will cost about $500, and they sit on standard mic stands.
For larger monitors ..... you'll probably need three - one in the back (drummer?) and two out front (singers?)
It's really a very personal thing - plan out the stage positions, and get the right tool for the job!