You don't mention required resolution - but if your planning on a DPO2002 perhaps 8bits is fine?
2 (channels) x 250Hz (max freq) x 2 (nyquist) x 600 (seconds) = 600,000 samples, this is close to the '1M' memory on the scope.
And you will probably want sample fast than Nyquist. I would suggest buying a much cheaper USB scope or even a datalogger, more memory and higher resolution.