To counter the effects of an amp sounding weak at lower volumes you're much better off putting an EQ in the effects loop and tweaking your tone from there.
:twisted:
+1.
With my Recto I used an attenuator in order to get it into it's "sweet spot" volume wise. I tried the EQ in the loop, but it wasn't working for me.
On the other hand I tried the same attenuator with a Mesa MkIII and I didn't like it. I thought the graphic EQ did a much better job of making it sound right at lower volumes.
In the end it comes down to using whatever works for you.
If it's just for band practice, consider throwing a blanket over your cab. It'll eat up alot of highs, but it's cheap and it'll save everyone's ears.