I own both a 40 and 20, haven't really ever noticed a louder hard drive on the 40, if you're going optical in it shouldn't be an issue. If you're doing line in I'm not sure, I've never ran line in on the 20. When I've done it on the 40 I've had the gain on the JB3 cranked up which produced some hard drive noise. As long as you keep the internal gain on the JB3 down hard drive noise shouldn't be too bad.