Laptops just don't perform like comparably-equipped desktop machines, because they have to be designed with heat in mind. That means slower CPUs and slower hard drives. Unless portability is a major concern, you'll get more horsepower for less money with a conventional desktop PC.
 
That's just a generalization, however. If you're maxing out all cores on your i7, something else is eating up those CPU cycles besides your DAW alone. Look for things that are competing with SONAR for CPU time. For example, make sure the wi-fi's turned off.

 Might be ok for smaller less intensive things. Was it running better earlier? Or is this the first time using Sonar on it?
 
Under powered computer and maybe also a software issue. Something could be hogging what little power it has, making matters worse.
 
The spec posted for the new computer looks decent for Sonar. As already mentioned it isn't nearly as good as you could get from a more custom build in a desktop form factor. If the laptop form factor is of prime consideration, then you could do much worse than this.

Thank you for the input guys.
 
I'll do some software checks but I can't think of an obvious culprit hogging the CPU.
 
My laptop was good for quite a few years but I haven't done much recording recently. Like I say, looping round the track seems to choke it but starts off fine. 
 
I guess I've just gotten used to using a laptop for the last 6 years but will look at desktop specs too. 
 
M

I updated the Nvidia graphics driver which was 3 years out of date and things improved considerably for the project I was working on :-) 
 
I can't see any other drivers to update unless anyone knows the usual culprits in this kind of thing?
 
Uninstalled antivirus and switched off wi-fi.
 
Thanks
M