i've seen only 1 or 2 production subsonic loads, but they kept the slugs within the normal AK weights (~150 grains). to get the most out of a subsonic load, i think you would need to load your own to get the heaviest bullet at subsonic speeds. if you are not trying to maximize distance, you...
try a saiga with a thumbhole stock in 7.62x39mm if you can find one (also called a Saiga 236 Pro Hunter). i ended up with a yugo underfolder after looking cause i came across a good deal, but the saiga thumbhole was my next choice. any of the saiga's are excellent shooters though harder to add...