Well I just did a recording and was going for a BIG guitar sound as well and to get that sound it took a couple of things.
1st we recorded both amps at the same time. Signal chain was Guitar-Radial Bigshot ABY- Amp 1 and Amp 2. Mic'ed using a 57. Dead center 3" off the grill then a LDC about a foot behind the 57. Provided the perfect balance tonally with the 57 getting the highs and the LDC getting the lows and adding some depth.
If I were you I'd try and get one more LDC as I don't believe the MXL will cut it for you although it may.