Exactly, I have a Two Notes Opus Modeler and went round and round looking at options.
I ended up with a Fender Rumble 100 combo, basically because I got it used for a great price.
I run the Opus into the FX Return and I can make it sound really good (it had a 4 Ohm stock speaker, which I upgraded to a Celestion BN12-300S (4) and that helped a lot), but when I listen to the same presets through some very good Sennheiser headphones, it does not sound the same as what comes out of the combo.
Which is to say, I wish I had saved up longer and got a really good active PA cab (like the QSC K12.2 or at a lower price point, the EV ZLX-12P-G2).
There are a few combos that will get you close to what a PA will put out (post EQ).