There are a number of possibilities for other cichlids in a larger tank. Heros work well ime. For me, larger, wild angels also worked well, peaceful medium acara sometimes-- if they're not too pushy, which also happens sometimes ime. I've seen different opinions on geos and discus in a tank-- I've seen people get varying results but it definitely works for some and I've seen the combination in some beautiful tanks. Sveni aren't fussy over current as long as water's kept clean with sufficient oxygen. They are pretty aggressive eaters ime-- and in past experience keeping discus, while they are leisurely feeders when allowed to be, they can also adapt to more competition for food, some of them better than others.
Partial excerpt of an article by Heiko Bleher, who has spent many years observing discus in the wild:
Definitive guide to Discus: part two - Practical Fishkeeping
What fish live with Discus?
I always noted the fish species and genera I also netted when taking Discus. I also tried to see far enough underwater to find the real companions of Discus, which are their visitors — and enemies.
The genera and species which live with them most frequently are Pterophyllum scalare and P. leopoldi, Geophagus spp. (pictured above) and Acarichthys heckelii, Satanoperca spp. and Biotodoma spp.
Heros spp was in almost every netting, then Hypselecara spp. and with Heckel Discus there were mostly Hoplarchus psittacus and Uaru amphiacanthoides. Mesonauta spp. was found almost all the time above the Discus, then followed Chaetobranchus and Chaetobranchopsis spp.