I'm not quite sure I know what you think the R2N does. It converts the RGB to composite or S-Video. NTSC or PAL is just related to the Hz of the output. "NTSC" doesn't refer to the video output type (ie, composite, S-Video, component, RGB).
Taking the RGB to composite with an encoder is actually worse than the normal Turbo composite output. The S-Video is better.
A word about the available encoders working with Turbo. They don't work. Well, at least. I'm trying to figure out why exactly. The best bet is the JROK but it's odd.
The best encoder? The one I make. And I'm not fluffing my own pillows. Don't need an additional RGB amp either.
I'll be posting more about it soon in fact.