I use my dynamic RE20 mic with Focusrite 2i4 preamp/USB-interface.
I have some noticeable hiss with this setup. The least noise I can get is when the gain knob is on maximum (which is not what you would normally expect). But it still can be heard.
If you search this mic on Youtube, you can hear that it can sound really clean and really noisy. For example, the video that features RE20 on the official EV channel sounds horrible, maybe even worse than what I have: https://youtu.be/ESuwVqvSsCk?t=5m15s
At the same time the guy who runs it through Neve 1073 DPD (a $2k preamp) sounds great: https://youtu.be/xkqFe6gft_s?t=8m3s
So am I right to assume, that preamp is what matters? And if so, what's the cheapest preamp to get rid of the self-noise?