[JohnM]

The 42-2540 stereo 1/8 to RCA cables are fairly short, so you'll need to make sure your soundcard is close to your receiver. You can also use this cable for the connection to your SPL meter, but the same caveat about the cable length applies - soundcard needs to be close to your usual listening position. If you use these cables for both those connections then you'd need 2 as you've listed (and your receiover would need to be close to your usual listening position), otherwise just one for whichever of the receiver/SPL meter connections is the short one. The 2-RCA to 1/8 adaptors can be a little bulky to easily plug in sometimes, but have the advantage that you can then run regular RCA - RCA cables to get from your soundcard to your receiver and SPL meter.