I just ordered the ARH LTs w/high flow cats. I was told by them that I would get 4 more hp with no cats. You may get a couple more since you don't currently have high flow cats but I wouldn't bet the farm on it. Hope this helps
You won't see any impressive gains from junking the cats, even coupled with cutouts/exhaust. You will however throw codes unless you get O2 simulators to replace the downstream sensor. Best bet is to get yourself a set of the magnaflow high flow cats which will out flow the OEM ones and weld them into place behind a set of long tube headers.