C. amethystoglossa gets very tall, but doesn't take up a lot of horizontal space (growths are usually pretty close together). It will still appear like a bonsai next to your grammatophyllum. C. jenmanii, as Tucker suggested, is a good choice for your location, as it's generally considered to be a warm grower. You might also try C. lueddemanniana, which is an outstanding species, and also a warmth lover.