Well I can tell you my Rect-O-Verb, which is very similar to the set up you are talking about is extremely loud if that's what you are wondering. It's basically what happens if you put a Solo 50 head on a 1x12 3/4 open back cabinet. During practice I dont turn it up nearly as loud as I could.
I use my Mesa 1X12 cab with my Dual for everything sept live shows. It has a black shadow speaker that says it will handle 90 watts, but I don't want to find out if that is true or not. It keeps up with our drummer so it should be O.K. with what your doing and to me it sounds just like a baby Recto without the bass thump. If I need more volume I set the whole shebang in a chair. Get One!
That will work fine. If you know what "Cone Cry" sounds like you'll be fine with the power rating. If notes start sounding a little hazy or worblie, back the volume down a bit. But that is crazy loud when that happens.