Do you want to use your amp and bypass the pre amp section or not use your amp at all? You can always hook up a pair of powered monitors to the outputs of the XT live. You can also run it through a power amp and unpowered monitors. If you have a stereo handy and a input on it you could probably use it too. How are you connecting it now? Through the instrument input on the amp? Or the effects loop?

I use an XTL, and finally settled on these setups...

At home, I bought some powered monitors, because I was fighting too much latency when I tried to hear things through my Mac with external speakers.  I have some JBL 2P monitors, and have just plugged in from the output jacks of the XTL into the speaker's inputs.  I didn't want to take up too much room on my desk space, so the JBL's fit the bill nicely,

At church, I tried MANY setups, much frustration, and far too much "tweaking" mixed with bouts of inconsistency.  I had a Peavey Classic 30, a great little guitar amp in it's own right, but not enough flexibility for the way I play on different songs.  So I needed to stick with the XTL, but playing through the Peavey just added too much distortion, had too much trouble getting a clean sound.  I read through some of the columns on here, and found a lot of people playing through the PA, but I wanted to have some stage volume because I play right next to our drummer (good, but LOUD).  I play both electric and acoustic, but not both in the same service...  so I bought a Genz Benz Shenandoah acoustic amp (basically, it's just a PA), and now get a LOT more clarity out of the XTL, no matter which flavor of patch I'm using.  Was lucky enough to have found the Genz Benz used at the Reno GC, so that helped price-wise ($400).

Look at some of the blogs here about the atomic amps, and you'll see the direction that I took off in.  A good acoustic amp really fits the bill for someone who is going to be using a modeler, and will double nicely when you're just playing an acoustic in a mellower setting.

Happy hunting.