If you want a contrasting sound to the Rytm, maybe something digital with an architecture not primarily geared towards subtractive analogue emulation…?
Perhaps an FM machine? DX7s are still pretty cheap. Most digital synths will do some kind of FM though.
I do love my Korg Z1, but the Radias is supposedly very nice and should also have architectural flexibility too.
Nord Modular G1 or G2 are fantastic though if you want a very flexibile architecture. It’s a huge shame that they stopped making them.