One of the primary differences between the different HP8753 models is the processor speed.? Newer = faster processor.? There are minor differences (like the addition of the disk drive on D and the LCD monitor from E onwards) as well.
I don't know the details regarding the speed issues, but things that affect speed include the number of measurement points and the IF bandwidth.? If you haven't already optomized these for your configuration you should adjust these for maximum throughput.
If speed is really an issue, you may need to upgrade to a newer instrument that will be orders of magnitude faster than the 8753.? There are really quick instruments that could probably address your issue for something in the 3-10K usd range.
