I have a Yorkville PA system with a seperate monitoring section....When I gig, I will probably put a wedge on both sides of me... And, if I want to get real serious, maybe a dedicated sub behind me....
Or a cheap way, would be to pick up a little 4 channel board... you know, one of those soundcraft "spirit" ones that go for about $150... Get a decent pair of phones that reproduce the bass decent enough..
I have tried monitoring my kit with cheap phones, and if you get cheap phones, they clip (or the speaker bottoms out) every time you hit the bass drum...... Which is why I mentioned decent phones...
My Audio Technica M40's are great, and never clip or distort.