i'm not sure how much you're willing to spend but swiftech has combined the
Apogee and the MCP350 pump
at $85 the block is almost free
the apogee doesn't focus cooling in one tiny area like the storm which should make it an ideal candidate for cooling your tricore
like ben said; you will probably get sufficient cooling out of any old block - i don't know the heat dissipated by the xbox
you might try using a large heatpipe/heatsink combination like this or this
one
both are very good and can be very silent