Watercooling rig - what order to put bits?

OK, my current watercooling kit consists of
Hydor L30 to
Swiftech MCW5000 block to
Wet and chilly P/A 55cm reservoir - then back to the pump

Now I'm soon going to be adding in a silentstar HD cooler into the loop.

Wondering is it better to put a Y splitter in after the pump so that HD and CPU get separate feeds, which then come back together befroe P/A reservoir

OR

run it in sequence i.e. pump - HD - CPU - rad and back?

I'm using 3/8" ID tubing throughout if that is relevant, and the silentstar will hopeful be using a 3/8" barb to 1/4 inch BSP connector. My graphics are passively cooled using a Zalman heatpipe wotsit.

Please note I'm not after the usual suggestions of increasing guage or stronger pumps or whatever - just want to use the kit I have most efficiently - I'm not an overclocker but a silence obsessive....

I don't see any advangate in running it parrallel rather than in series. The HD will add very little to the water anyway. If you really must have the coolest water to the CPU, have the HDD block after the CPU, as the HDD doesn't really need it.

This is how it should go:

Pump > CPU > HDD > Rad/Res > Pump

I think you may be over-rating the P/A Reservoir, i would always run a radiator in the loop. My mate uses a Thermochill 120.1 with 2x 55cm P/A Reservoirs and the reservoirs only drop the temperature ~4°C. There's only one way to find out but that's just my 2p :)

But he just love silence so i guess that's not a prob.

If it is silence he's after than it should be fine, i imagine the temperatures will be similar to air cooling with a stock HS/F.