speechsynth voices?

[Miku]

Is there such thing as additional voices for the FL speech synth I can download?

[Xelebes]

No, but there are other programs out there that you can use. Some, if not most, you'll need to buy but there are some free ones that are fun to use. Best one is using an Atari emulator with STSpeech - you'll get those classic Das Boot vocals from that one.