Check out the link in my sig if you want some inspiration, I think you'll really enjoy the change (at least for a while), I certainly prefer my tank now than when it just had the arowana and a few cichlids. It's 240x120x70cm, so only slightly larger than yours, here's the current stock;
3 Geophagus altifrons, ~8-9"
4 L190 royal Panaque, ~9-10"
3-4 smaller misc plecs
8 Pterophyllum scalare
4 festivum
20 Corydoras sterbai
20 lemon tetras
and in quarrantine 6 L18 Gold Nuggets and 6 more tiny altifrons. I'm also planning on adding more tetras, possibly columbians or more lemons
I wouldn't suggest neons as they don't do so well at higher temps favoured by the loaches, but there are loads of mid-sized tetras and barbs that could work in that sort of set up, just make sure they're not nippers if you're going to keep Geophagus. I'd siggest you go for 6-10 of the Red Heads as they're one of the smaller species, they'll look great in a big group in a tank like that. With Geos and Clowns you'll want to look for something to bring some activity to the upper levels of the tank, angels or festivum (or both) are good for this and will fit with your peaceful theme. Alternately just go for a massive number of the schooling fish!
You'll also want to change up the aquascape from when you had rays as you won't need such a big open area. It's still good to have plenty of room at the lower level for the Geos to do their thing, but you can take up a heap more room in the mid-upper levels with tall twisty pieces of wood, which will make the mid-swimming fish feel a bit more comfortable.
