The price of an external preamp may vary from 80 USD per channel to 3.500 USD per channel (as the acclaimed Neve 1073) I strongly suggest you to use an audio card that includes mic preamps because a 80 USD external preamps it doesn't sounds better than the equivalent in a 150 USD audio card. In this way you have to buy only an external audio card (as I suggested in my previous mail) as Steinberg Ur22, or Focusrite Scarlett, or something from Avid/M Audio.
By the way a simple 1 channel mic/line preamp that I've used to use is Golden Age Pre 73 MK II, is a chinese clone of the 1073, here in Italy with a price tag of 300 euros so I figure USD 350. It was a good preamps to my taste, not a Neve or a Millennia but usable. Another very good external preamp, a bang for the buck, is FMR Audio Rnp, 2 channels mic line preamps from Texas.
These days I haven't a studio, anymore, and I use a little Zoom H6, it's a portable 6 tracks, it has 2 condenser mics, it's an audio card (with mic preamps) it's so many things, check it out. Its audio quality is good.
Ciao