Maybe try placing it somewhere that you can cover the cabinet with a few heavy moving (shipping) blankets. Or whatever.
And mic the cabinet with the entire mic and amp covered.
I hope this suggestion makes some sense.

Or you can get the isolation cab by Randall.

Both suggestions make sense. The blanket theory works if you don't need TOTAL isolation, because it allows for you to vary the amount of "air" around the cab and the mic. If you use "hard walls" encompassing the rig, you tend to get a more "nasally", "boxy" sound out of it. And it's easier and cheaper to do, as well. Just grab some boom stands to make a "frame", and throw the blankets all over it.
I have had a Randall box for a while. Don't use it as much as I used to, and when I do, it's usually at a church that needs to contain the geetarist.
Sounds OK, certainly holds down the volume, but the tone isn't all that great or variable.

unsure if this is any help , but ussually in my studio ( i have two rooms one main room and an isolation booth for drums) anyhow I ussually put everyone in one room , di some stuff put the drums in the iso booth, and then I run a lead to an amp down the hall way out the door , that ussually helps, (ussually I put the amp in the coffee room ! ) anyhow its outta the way of everybody else, dont know if you can pull that off in the basement, all yah need is 1 freaking long 1/4 and one freaking long xlr cable for the mic.

gil

EM just ran an [[url=http://[/URL]="http://emusician.co…"]article about this[/]="http://emusician.co…"]article about this[/]. For me, if I need isolation (ie, no amp sounds in the drum overheads) then I just record basic tracks with a Pod and then overdub the amp stuff later.

I recently started putting my 4x12 into my wife's closet, which is stuffed with clothing. Works like a charm.

Great suggestion. I once knew a guy who did the same with his closet. He could jam his half stack LOUD. And it was hardly heard, even standing right in front of the door.
I could tell he put some time into sealing off the closet for good isolation. And it worked darn well.