Absolutely, yes. We started out with sound support philosophy from the Buddy Holly era...vocals got the lion's share of sound support, with the kick drum and maybe snare/toms. Guitars/bass were on their own. Then we were playing bigger venues, outdoor gigs, etc. and really pushed the limit of our self instrument monitoring. In those situations I rarely could hear my own vocals. That's when we started a mixed bag of self amp'ed guitars with IEMs for vocals. Man, what a failure! We couldn't control what each person wanted and now I couldn't hear my guitar. LOSE.I am also an advocate for in-ear monitors if your band can afford them...if you and the other band members can actually hear each other in practice and on stage, aren't you going to sound a whole lot better? And play better? And be tighter?
There's only one one way to do sound support: all or nothing. All IEMs replacing floor monitors, or none. All instruments in the mix or go home. We did it for almost 4 years so I can confirm that it can be done, but it was a seriously difficult task. Spend the money to do it right, get trained by a professional, and don't look back.