Adding a second pump improves flow.
Whether the extra heat from the pump offsets the benefits of the extra flow is another question.
Here's "a" PQ graph for the 1300:
http://www.wcaquatics.com/cgi-bin/it...aqua_pump.html
I've not got approximator to where it needs to be, but the closest pump to it appears to be the Laing D4 which can push the same LPM but can handle more head, and the MCP350 which can get the same LPM but not as much head.
Anyway, I've used a MCR320QP rad and have not factored any tubing (coz its broken) and have used 2 x Apogee blocks , 2 x MCW60 blocks and 2 x MCW30 blocks. The Laing D4 gets over 4 LPM which is certainly enough, whilst the MCP350 gets over 2.5 LPM which should be enough.
Averaging suggests the 1300 would get around 3 LPM which is enough.
I'd almost be certain any extra flow from a second pump would be offset by its heat and not make a noticeable gain (or something like half a degree).
Far better to put a second radiator in for that much heat...