hey biff.....Looney tunez gave you good advice...
Couple things you could try in addition to that:
Ideally three mics would work well.....But you should try all of the following even with just 2 mics.
For the close mic technique for the in your face ballsy sound....Couple of different options here.....You can place the mic so it is actually touching the grill cloth or go for the six to eight inches away technique....Also try placing the mic on the parameter of the speaker cone.......always off axis, like looney said.
Secondly, Try a mid range mic.....one anywhere between 3-6 feet away from the speaker giving you more "room" and less detail.
and a third anywhere from 10 to 20 feet away for the room sound..... Try raising this far mic about 4 or 5 feet off the ground..
You can combine all three of these and mix them any way you like inorder to get many different sounds.......Since you don't have three mics I would try both the mid range mic and the distant mic in combo with the close mic and see which one is most successful in capturing the sound you want.
Also experiment a little....move your amp around to different places in the room.....you could also try raising the amp off the ground....there are a million different things that you can try and an infinite combination of those things that will work....
*note* there isn't one way to do anything...these are just some of the things that I routinely try...
Good luck