Xotic effects makes some great stuff. I used a boss Super overdrive ala zakk wylde for years and it worked well. I also have the Xotic BB Preamp and it is much more versatile I would say, but a bit more expensive. The MXR Zakk wylde, speaking of Zakk, is great and has a bunch of useable low end. Misha Mansoor recently came out with the Precision Drive specifically for pushing the front end of an amp and it sounds pretty phenominal. Im with Jake though, save up for the Axe FX. Ive had the Axe FX II XL for a few years and I dont think Ill ever go without an Axe FX again if I can help it. Im selling my whole Axe FX II XL and MFC 101 Mark III rig with 9 cab packs now so I can upgrade to the Axe FX III, but the truth is, tonally the II is every bit of good as the III right now and I dont really NEED to sell it. But yeah man, that fractal stuff can do basically anything you want once you know how to work with it. Tone for days!