It is possible that the interface is connected, but not pointed to in Sonar, and also he could be using WDM drivers, rather than ASIO.
 
What do you have the Driver Mode set to in Sonar, and what device are you pointing to? (ASIO or WDM, and audio interface or sound card)
 
What is your Sample Rate in Sonar, as well as the setting for the audio interface?  (They must match)
 
What is your ASIO Buffer Size set to for your audio interface?
 
If you are not setting Sonar to use your audio interface, you should, and also try setting the Driver Mode to ASIO - taking advantage of your audio interface drivers.
 
Bob Bone
 

WhiteSheet
i wanted to know if having more RAM can solve this as the plugins will have more to work with
or if a better soundcard (and btw i'm using an mme32 i think) would help

You have a decent sound card (audio interface), but you are using the worst possible drivers for it. ASIO is your best option, or even WDM. Anything but MME. That may not be causing CPU issues, but it still needs to be addressed.
 
Don't even bother with more ram unless you upgrade to a 64 bit OS - and install/run Sonar 64 bit.

codamedia
 
You have a decent sound card (audio interface), but you are using the worst possible drivers for it. ASIO is your best option, or even WDM. Anything but MME. That may not be causing CPU issues, but it still needs to be addressed.

Download the latest drivers here:
http://www.steinberg.net/en/support/downloads_hardware/downloads_ur22.html

I am not sure if I caught everything in this thread, but wanted to throw a few things out for thought.
 
You mentioned you tried "ASIO" but wanted to hear other things too. There are two points with this specifically...
1) ASIO is the most efficient CPU/latency usage you can get, so please consider this when you are trying to cut down on CPU. ASIO (and WDM) drivers, bypass the windows kernel, so streamline audio and CPU usage from that alone.
2) As you realize you have CPU issues, throwing another driver mode (particularly MME if you are using that) into the mix is "just asking for pain."
 
A second point is latency and I/O buffers. Have you adjusted your interface latency and I/O buffers for X1? This is an important step and is system specific, and should be done any time you make a change to the system.
 
Just for clarification, can you please let us know what driver mode you are using with X1? If I missed that someplace, I apologize. I saw MME, but please clarify this (that is the absolute worst choice you can make for driver mode). Research and read up on "ASIO/WDM versus MME."
 
Edit: I glazed over codamedia's response to you... so think MME is correct.