Solved: Replacement Antennae for 2-Antenna Router?

Hi guys,

I don't get the best wifi signal in my house. So I bought a giant D-Link antenna and that solved the problem pretty well. My router eventually died and my ISP sent me a new one. This one's a new model and has two antennae instead of one. The signal is really weak and doesn't get to all of my rooms. I can just buy another D-Link antenna and use those to boost the signal, right? Can I mix manufacturers and models, or should I get a matched pair?

Thanks!!