Just purchased a new klipsch 12inch sub to replace an old JBL 10inch. Question can I run the JBL10 inch alone with the Klipsch 12? Looking at placing them at opposite sides of the room. I really love the Klipsch but hate using the JBL as a piece of furniture. I have the Yamaha 663 receiver will it make the two sub's compatible.

Yes, you CAN use the JBL as well. Just use a y-cable from your receiver's subwoofer out and run a cable to each sub. Two subs can help even out bass response in your room. Unfortunately, using two subs with different capabilities (such as the Klipsch and JBL you have) can sometimes cause more problems than they fix. For example, if the JBL tends to sound less refined than the Klipsch, you can end up losing clarity if you use both subs as opposed to just the Klipsch. Also, using subs with different deep extension capabilities can tend to augment certain frequencies while leaving others too subdued. My recommendation is to spend a few bucks and get the cable(s) you need (please don't go to Best Buy and spend $100 on Monster cables - you can get everything you need from Monoprice.com for probably around $15) and try it for yourself. Then decide whether you prefer running both subs or just the Klipsch.