I think I'm going to go with the 5153Red...
changing amp type is not as straight forward as you think when your presets work like mine..
when the EXP is heel down, the amp drive will be at it's min value to help clean up the tone..
the min value for the 5150 is much louder and a little dirtier than that of the 5153Red..
also, as the EXP moves to the toe down position, the 5153Red dirties up more gradually
this means that - as I have two amps running simultaneously, the VH4 will dirty up more quickly..
so right now, as the EXP moves to the toe down position, the VH4 on the right of the mix gets dirtier and louder sooner..
this means that at the mid point the 5153Red is still quite clean and soft, and the VH4 is getting quite crunchy and is far louder..
this of course needs sorting out cos it sound crap...
but to be honest, I expected this.. in fact, when I set up the preset with the 5150 and the VH4, I did quite a lot of work to find the right modifier curves so that they dirty up and louden at the same rate..
when you change amp type you should expect it to have completely different charateristics in this respect...
so.. I need to noodle around some more with the VH4 and 5153Red modifier graphs to re-align their "dirtying growth rate"..
I've also found that the 5153Red is a little less fat than the 5150..
so the amp's depth and EQ page controls will get a bit of a nudge..
if I don't do this, I will have different levels of low end between the VH4 [panned right] and the 5153Red [panned left]..
the lack of low end on the left will make the preset pull to the right in the stereo image..
although the whole point of running two different amp/cab combinations is that their differences combine to grenerate a 'bigger' resultant tone..
it is very important to [as best you can] have each amp generate the same amount of low end in roughly the same frequency range...
this is just a case of listening and tweaking... it's well worth taking time to get this right...