I had a lot of fun playing larger SCW battles using Peter Pigs 'Square Bashing', although I expect Great War Spearhead would work fine too. Both use 1 base = 1 company/battery/squadron, so are quite large scale.
I did a variant of AK47 for brigade level battles, which worked OK too, and I've run the odd very large sale game using operational rules such as Megablitz (1 base = 1 battalion).
I've mainly been playing SCW recently with Neil Thomas's One Hour Wargames rules though (Machine Age Warfare section), which have the merit of being fast and fun, even if not hugely 'realistic'.
Cheers
Martin