J4R10
But if the X3 is coming this fall, I'm pretty sure that the upgrade costs X1 users $200-$300. Then it's time to make a decision between Sonar and Cubase.
By all means, give Cubase 7 a whirl. Has many great features...
Also has some weak areas (which I mentioned above).
You'll make some compromise either way...
Currently you can upgrade from X1 Expanded to X2 for $99.
The upgrade to X2 from X1 is $119.
If you wait for the "sale" (right before release of a new version), you typically buy the current version with a free upgrade to the next. If things stay the same, you'd be able to upgrade to X3 for ~$100.