Presumably, you've got separate lines for the molex connectors and the sata connectors coming off of the drive. If you have to split the power to handle the number of drives, even on a single rail supply, you really want to balance the load between those sets of wires from the supply.
You don't explicitly specify the model # of the supply, but if its a CX430, then you've got 32A on the 12v line available when the supply was new.
Round figures, you can count on a drive taking up ~2A during spinup's, so if/when all the drives spin up together (parity checks / rebuilds, etc), then you're drawing 20A. But you also have to remember that the CPU also draws from the 12V rail, and depending upon the CPU it can pretty much be 8-10A itself when not idle. So you worst case scenario is a draw of around 28-30A on a supply that can handle 32A when new (and as supplies age they cannot handle their rated draw).
Entirely up to you, but IMO the supply is a bit small to handle 10 drives.