Wow, I'm really thankful for all the replies.
I'm definitely going to check out the Ironball and the LBX - there's a lot of love for those on here, and I'm pleased because the Ironball was on my list - it validates my thinking!
The LBX needs to be tried too. I'm in London this weekend and will have a a go on a Mark v:25 and hopefully will find an LBX somewhere to try too.
Thanks all.
For anyone looking for a non-high gain lunchbox head - I cannot speak highly enough of the Laney Lionheart L5H, it really is INCREDIBLE! Clean's to die for and make a perfect pedal platform and there's a nice drive channel on there too.