There are 4 cpu cores with 2 hyper threads each though and blitting graphics is a ridiculously parallelizable task. So if you “own” those routines rather than relying on a library there’s much that can be done.
As for using the gpu instead, not knowing any details of how text rendering is implemented in ST2 couldn’t you just cache the glyphs to 1 or more altas textures and blit using gl?