960,000 sps will work fine with one VCO. The higher sample rate is more important when you have two or more VCOs. To maximize usable bandwidth, you will want 2.4 or 2.56 msps. For any set of channels more than 2 Mhz apart you will need a second SDR.
Thanks for the reply, but just one more question, does the age of the computer make a difference? I have a copy of your program on two laptops, one more powerful than the other.