It really depends if he is looking to do more experimentation with stuff, and roll his own, or play with various gear that might work or be writing his own custom code and debugging that OR if he is looking for a new tool that will give him the data he needs to do the task at hand. This dosnt seem like an application where someone wants to deal in maybe's
It seems to me he is looking for the latter. Cost wise, yea some of the options could be cheaper in capital outlay, but once you factor in your time, probably not so cheap.
In my own personal experience, I was able to acquire a nice OLD 2 channel DSA with a GPIB port, and an NI GPIB to USB adapter pretty cheap, and frankly has paid for itself 10 times over in time savings. It has its place.
The other thing is that if you investigate other documented issues and testing of such issues, they will most likely be talking about DSA functions, analysis and results. Past research for such things was most likely done with DSA's
a DSA with 2+ channels is really the way I would go for all the above reasons, and if you need to go cheap, get one off ebay that's backed by someone reputable.
again, not that you cant get away with doing it other ways, but, you will always be fighting the equipment to get it to do what a DSA does out of the box..