@Mr Perceptive (and Samuel):
You have (at least) 2 variables in 1 equation. The DTS-HD MA sound on some Blu-ray discs (not Blue, btw) is a huge improvement over the DTS (SD) track, while on some discs they are only marginal better. If you take one of the latter discs, you'll probably find the sound coming from your Meridian better, while if you would have taken a disc with a huge difference between the 2 codec's, you could find that the DTS-HD MA sounds better (even though it beeing processed through the Onkyo). This all depends on 'how much' the DTS-HD MA track sounds better relative to 'how much' the Onkyo sounds worse.