As above,the tops you have won't support a full band mix at the volume you'll need in most venues.
If you add at least one sub, and better two,then it's a different story, as most of the lower frequency stuff that makes up the kik drum and bass will no longer go to the tops.
This is the way I do it, with everything through the P.A and small ish backline (I use an svt410 but I have a large van,for small gigs I get by with an Ashdown mini 48 and an Ampeg PF500).
It's a compromise really, as you have to carry the subs, but In my opinion a full mix leads to a much better sound in general and helps to keep that backline at reasonable levels.
I reckon you could easily get away with a half decent 150watt combo so long as you don't load the tone with too much low end and push the mids a little for cut.
Remember your tone out in the front will be EQd differently to suit the rig and room.
Also,if you have the kick drum in the rig, you'll need that sub anyway.
MM