Frankly, except for perhaps some very simplistic, low budget models, there really isn't all that much difference in complexity among the consumer class of wireless routers. They all work pretty much the same, have the same features, are configured w/ the same tools, etc. So take your pick.
As far as extenders (aka repeaters), it never hurts to use the same brand, but given that these products employ wifi standards (G, N), as long as you get an extender/repeater that uses these same standards, it won't really matter. Such products will usually be called "universal" extenders/repeaters to indicate their broad compatibility.