If it's within your budget. Take whatever pumps you have back to the store and get yourself 1 mp10.
If not, then 2 425's I think would be better as it would help create more random flow then just 1 on one side.
I'm no expert though just giving you my opinion.
"When creating an aqua scape, strive for the beauty of imperfection, as its art and there is no wrong or right, it's left open for interpretation" James Findley