Apparently a grid of component heat vents and reactor heat exchangers does quite well.
I got 140 EU/t with an efficiency of 3.5:
http://www.talonfiremage.pwp.blueyonder.co.uk/v3/reactorplan…62e0iucjyhfjdvk
Also, you can just add two more heat exchangers and another cell or two (depending on placement) to get a bit more power at the cost of efficiency.