I was downloading some presets and trying them out when I stumbled upon this set of presets provided by the wonderful Mr. Tyler Grund. This SRV patch nailed that sound so well I just had to record it. Playing is a little sloppy, but I just love the way the Axe responds when you hit those low strings really hard. This box is simply fantastic. Patches:
http://tylergrund.com/axefx2.html
The basic patch centers around what Stevie Ray Vaughan really used: A Fender Vibroverb cranked up. Master and gain are both at about 9. Treble and Mids to about 6. Bass to about 1.5 - very low. Add some spring or room reverb and you're there. Put a Tubescreamer in front with the level and tone cranked, gain down low for a boost. Tweak the speaker IR cab until it sounds right.