Fournier HTA-2 is a hand built tube hybrid headphone amplifier, they were hand built in the U.S.A and sold on ebay for roughly 200$. They were reviewed with high regard and considered to punch above their price range.
Audio Poutine CDAC+
This is a diy product very similar to the ODAC, and though the internal is mostly similar there...
TOTL Universal In Ear Monitor from Audiofly, 6BA Drivers in each earpiece
Stoner Acoustics UD110 V2
Stoner Acoustic's second version of their second budget model which was just an updated version...
Gemini Doctor WS 1.2 Blue Bird Portable Amp
Product Details Model: WS1.2 Product Dimensions: 24mm*81mm*57mm Weight: 0.16kg Output Power:...
Acoustic Research AR-H1
Planar magnetic headphone, lightweight, great build quality, relatively comfortable, balanced sound quality.