Bottlehead Crack + Speedball OTL Amplifier is available for $299. Select Bottlehead Crack for $199 and add the Speedball upgrade for $100. Regular price for Speedball is $125 (total $399).
This is one of the best amplifiers available for high impedance headphones (>250 ohms). Perfect for those who bought the Sennheiser HD600 and HD650 in recent deals. This is a DIY kit and requires assembly and basic soldering for the Speedball.