HI,
There are quite a few nice choice for recording Mic for under $300 now.

If you want a condenser Mic then Rode, SE Electronics, Sennheiser, AKG and Shure all make nice ones in the under $300 range that will work great with the Fireface.

For a Dynamic then I'd looks at the Shure Beta series or Audix.

Thanks Chris

i assume if i choose a mic like BEYERDYNAMIC TG V56C [condenser vocal microphone, cardioid, 40 - 20.000 Hz, 190 Ohms, treble boost for transparent signal] i might be alright with the vocal signal? i mean 190ohm mic should give significantly higher signal than 600ohm mic i tried?

Ah, +12dB gain on my Babyface was fine. +15dB gain I could go into the red if singing loud (and that may not be all that loud), and at +18dB gain on the circular knob I was peaking into the red more.

That is with the Sennheiser Condenser Mic listed above (the MK4).

But there are other similar mics also there so a salesperson may have something even cheaper that works just about as good.
If you want better quality like some people do - then prepare to spend $1000, otherwise, you will have to look at the different mics or get a preamp.

And there is a reason for a preamp - if you want a tube sound - and replacing tubes in the end when the volume goes down again (the tube worn out - dead.)
http://www.sweetwater.com/store/detail/TubePRE/
have not tried it, so I do not know.
Look around, that is what the person in the store is for - more familiar with all the different equipment out nowadays.

There is an excellent article discussing microphone and preamp interaction located here: http://www.rane.com/note148.html

The hardest thing to get over is that fact that the input is automatic. TotalMixFX is only for listening to the signal, not controlling the input, only listening. RME stated that, and out of habit I guess I been going along and thinking I was controlling the input, when I am only controlling the listening. So if you are turning it up that far to listen to it, then the input of your mic is really really weak, and you must have the gain up there going into the automatic level inputs first of all.
I wish it was either, manual or automatic, because I like to tinker around. Have to look at the other RME audio/interfaces and see how they are, just to be curious.