Affordable side scan software options

[zslnk]

Hi
I'm looking to piece together an old Klein system 2000 digital side scan system that has no topside box. Basic outputs are analog or digital and trigger signal. I'm an EE that works on custom ultrasonic systems but this is for my personal use and my first sonar project.

The challenge that I see is finding affordable software. I've made a few calls and 10k$usd seems to be the norm. I've heard about some other cheap options but cant track anything down. What options do I have?
Thanks
Z

[zslnk]

Pretty quiet in here but I'll provide an update:
I purchased a non-functional Klein System 2000 with fish, cable and transducer box. The topside box was an easy fix as the dead fish was caused by an 'open' wire wound resistor. I purchased Hypack Marine Search (2500USD) and using an NI-USB6221 I sample the analog outputs on the transducer box. It works very well. It's too bad that I'm having to convert the digital to analog then back to digital but I couldn't find software (save for writing my own using labview) that could interface to the system 2000 directly. The topside box does have a digital 12bit output that is very simple to decode. I find the Hypack a bit clunky to use but it works once you get it all talking.