I have two amps out of your list, El Diablo and VH100R 8)
El Diablo is a great amp because it can achieve both Marshally thrash sounds and Mesa saturation and thud. Probably because of its active EQ and the tube contour control. It's got loads of gain and it works very well with the GB Gflex cab, unsurprisingly. I find that with normal cabs with the gain up it can sound a little muffled. The voicing is different to other typical amps but I personally quite like it. Played it again last night and thought this thing is a monster! :twisted:
VH100R is a more organic sounding amp than the El Diablo, although it doesn't have as much gain (never thought I'd say the Laney doesn't have gain!). It will not do "perfect" Marshall sounds if that's what you are after, in that case get the JVM, but it can get close. If you can imagine a smoother, more rounded, thicker Marshall sound you'd be close. I think the sound of Paul Gilbert, modern Sabbath, and Mastodon are good examples of how Laney VH100R can sound.
I am currently considering selling my El Diablo though, because I just bought a new guitar (not telling what just yet

) and need to get some cash quickly! If you are interested drop me a PM :)