Yeah, getting THE sound you want can be a little time-consuming... Usually takes me a couple days to tweak 'em throughly, play with it one day until I can't hear the differences, quit and come back next day or so, repeat as needed.
One band I play in is an ABB trib band (Idlewild West, shameless plug) and I do the Duane stuff and keep trying different profiles trying to hit the At Fillmore East tones (as I recall, Duane used a '69 or '70 Super Bass with, I think, JBL- loaded cabs, not exactly standard Marshall cabs), I've gone through through a bunch of profiles, Marshall Plexis, Super Leads (though I have yet to try r-u-serious' profiles, I will audition them tonight), also the PRS DA, but turns out the closest I found was the freebie Marshall DSL40, which I also just happen to own and was using just prior to buying my Powerhead. Maybe I'm biased, but with some tweaks it gets pretty danged close.
Another little factoid I thought I might mention, to add to the discussion: my "Dickey" partner in the ABB trib band uses a meticulously-tweaked Digitech RP-1000 into the clean channel of usually either an Egnater Tweaker 40 or a Mesa Nomad 45 and he gets great tones (sounds like crap when he goes direct from the Digitech, however). He really likes the Kemper, but he is happy with the Digitech/amp combo and doesn't want to shell out the bucks. Just goes to show more than one way to skin a cat.