I agree with many of the guys here that the E-Z Command is a fantastic little system that is great for beginners who just need something that works - and works well.
Based off of what your current desires are in your system, I would personally suggest the Digitrax Zephyr. It's an all in one system that has ways to accomplish what you'd like. You can still use your power booster with it - I would really recommend it anyway, as power output is the only real complaint I have had with it.
The Zephyr system has connections that allow you to connect up to two standard DC controllers to, and basically use them as throttles for two different locomotive addresses. The button on the Zephyr that controls this is labeled 'Jump.' This includes the '00' address that allows the operation of DC locomotives, just as button 10 on the E-Z Command - or when you connect the secondary throttle. (I've done it - mainly because when you do it allows you to use button 10 as a standard DCC locomotive button instead of the analog control.)
Based off of what your current desires are in your system, I would personally suggest the Digitrax Zephyr. It's an all in one system that has ways to accomplish what you'd like. You can still use your power booster with it - I would really recommend it anyway, as power output is the only real complaint I have had with it.
The Zephyr system has connections that allow you to connect up to two standard DC controllers to, and basically use them as throttles for two different locomotive addresses. The button on the Zephyr that controls this is labeled 'Jump.' This includes the '00' address that allows the operation of DC locomotives, just as button 10 on the E-Z Command - or when you connect the secondary throttle. (I've done it - mainly because when you do it allows you to use button 10 as a standard DCC locomotive button instead of the analog control.)