Yeah, it sounds awesome as a preamp! I think a lot of people who aren't impressed by what it can do direct through impulses would love it through a poweramp and cab. It's important to use a good poweramp too though.
See, I love the SE. It's been my dream amp for a while, but never could afford it until recently. I finally got a chance to snag one for cheap -- $2000 including a roadcase... that's ridiculous for a head that usually sells for $4000 new or $2800 used. So, for sentimental kind of reasons, it's only $1300 more (say I sell the VHT for $700) to have the ability to have a real amp along with the axe-fx instead of just axe-fx + poweramp. That's really not that bad.
Of course, it depends on the price..... for a Diezel or even what the SE normally sells for, I'm not sure I'd be willing to do it because of the price difference... would probably just stick with the axe-fx + vht. I don't know though. I try not to drag any sentimental kind of feelings in there and just stay objective, so I still want to spend time with the SE/Axe-FX/VHT and see what conclusions I come to just using my own ears and judgement and seeing what I really think sounds better to me.