I can give you a more practical response. I did what you were asking. I used to run a RT 10d with a Rel sub. To me it was not sound I was looking for. I went with a pair of JL 112's which sound great. A pair of good subs really did it for me. My advise is to get a better sub see how you like it. Then get another matching sub if you are not completely satisfied. Setup is important but a good quality sub is going to make a huge difference. There are a lot of great subs out there. Once you hear them you will see where the klipsch comes up short.
Best setup for two subwoofers.
I would like to run 2 subwoofers in my home theater setup. Currently i have one Klipsch RT-12d, which sounds great, but I would like the depth of bass to be "over the top". Will it sound good to mix and match types and brands of subs? I was looking into a Velodyne 18dd or sig 1812, but am unsure how well it will work. Should i just add another Klipsch or can I use something different altogether? Im kinda new to all of this and just wondered if anyone else can share any ideas.