Choosing a mic for jamkazam

[Val]

I sing with a couple of friends and they're constantly telling me to be louder.  We've adjusted all kinds of settings but the problem remains.  I have a SHURE SM58, (currently on a desktop stand) and find I have to almost eat the mic to get a satisfactory volume.  This gets in the way of my guitar, which already bangs on my computer desk. 
Can anyone recommend a mic that I can use at a greater distance? I'm willing the spend the money within reason.