Here is an alternative. There is a British company http://www.ced.co.uk
which makes data acquisition interfaces for electrophysiology. The interfaces have TTL I/O, ADCs (of course) and DACs, and they are programmable, i.e. they have own processors that can run simple programs with timing closely coupled with data acquisition. You can program them to respond with DAC output (e.g., audio) to a TTL pulse from a pressure sensor (or ADC input crossing a level) within tens of microseconds. However, you would have to spend about $5,900 for the cheapest interface and probably $2,800 for software (the latter unless you want to go into low-level programming of the interface), and many of the features could be of little use for you, e.g. spike sorting capabilities. You may also need a low-pass anti-aliasing filter because their DACs are unfiltered.