I recently began experimenting with different microphones at the station. So far I have acquired Radio Shack "Grayline" and Electrovoice RE-27 microphones, both were purchased used off of ebay. The Grayline was about $20 and the RE-27 was around $300. I've received good audio reports using both microphones straight into the transceiver without any outboard processing, but the RE-27 does seem to out perform the Grayline most of the time. I've installed a Heil DT-1 desk top flush mount on the front corner of the desk which allows me to use a boom/shockmount combination, or I can easily remove the boom without any adverse aesthetics. I may invest in a outboard processor later on if I run across a good deal, but it is low on the priority list.
Here is a photo of the RE-27 on the boom...