I have a Studio Projects VTB-1 preamp for sale for $100 shipped. It's barely used, and it's regarded as one of the best inexpensive preamps. I just am upgrading to an interface with 8 built in preamps so I'm letting this go. Shoot me a message if you're interested.
Electro Harmonix 12ay7. Total sleeper hit. Real tube Pre. Not starved plate. Love mine.
I've got two of these and use them with condenser mics for acoustic guitar and vocals.
If you choose this, be aware that the output is quieter than many preamps. You may want to not use this preamp for quiet sources when recording with dynamic mics.
I've got the MPA Gold, the Studio Projects VTB1 and I've experimented with the Rane pre mentioned above. They all get the job done well in slightly different ways.
One preamp not mentioned that I've spoken about here a bunch of times is a symetrix sx202. No frills, 2 channels, clean strong gain. I think it's got something special about it. You can get one on the used market anywhere from $75-$125.
No frills pre for me would be the ART stuff. But if you just want clean gain then get a Mackie 1202 or like. Not the greatest pres but do the job. Also these are great little toolboxes to have in the studio.