umm just some thoughts or possibilities - super dark crystal malts (80-150L), smoked malt, brown malt, amber malt, roasted wheat/rye (the lovibond is roughly the same as choc-RB, but at least it's a different grain)
i guess i'd use the above grains for my main flavor contributions and then bring the srm to the bottom of the range with the black malt. btw i make most of my stouts with a 50/50 mix of black malt and roasted barley (note that i'm a huge fan of black malt)
obviously you'd have to play with the percentages. cheers, j