looking at a new laptop for location recording. I have recently downloaded info on minimum speed recommended for X1 Producer (I know "old !") as intel  2.67 GHz.  A lot of processors I have seen are 2.1 - so will this make a noticeable difference or glitches?? It runs fine on my desktop - but that is 2.7-2.8
 
Thanks

More important than clock speed is the processor type. Clock speed by itself not mean very much.

Well I found one that is AMD A6-Series    2.1 speed 

or :  

Intel Core i5 2.40 GHz 

For recording you might need to check the disk speed requirement with respect to number of tracks playing/recording.

Yeah, it might be a good idea to discuss the laptops your are looking at rather than just the CPU. You will get more intelligent feedback about the suitability of your choices.

I'd suggest looking at maybe slightly slower quad-core i7s to get the extra cores/hyperthreading rather than a slightly faster duo-core.

The overall performance of all the PC components combined is at least as important as the cpu speed though. As is whether you use lots of resource-intensive vst instruments or not.

The days when you could have a meaningful specification based on simple clock speed have passed. Unfortunately you still see it commonly in "system requirements" lists, even though it does not make a lot of sense. Even less useful to most users is something like "Intel Core 2 Duo E8200 2.67 GHz/AMD Phenom Quad Core 9750 2.4 Ghz".  That seems to indicate that only one CPU will work, and how do you know if a newer CPU is better? Even more confusing is that one CPU can blow away another in a math contest, and be slower in a database task. To see how performance compares, you can look at benchmarks, but that benchmark needs to match the use you plan to be truly predictive. That said, the Core 2 E8200 is now a pretty old CPU, and almost any decent quad core (or better) chip will be more efficient for most of what you will do in Sonar. Other factors besides the CPU power may make more of a difference in how well Sonar may perform, and in laptops especially, which are often designed to permit only limited configuration changes, a powerful CPU is no guarantee of success.
 
http://www.howtogeek.com/...-computer-performance/
https://www.cpubenchmark.net/
http://www.adkproaudio.com/benchmarks.cfm
 

I have two desktops.  My primary system is an i7 3770 and my backup is an i5 3550.  The i7 was down for almost a month for warranty service on the motherboard and I used the backup i5 system.  For Sonar (X3 at the time) I saw no difference.  However, I'm not doing any MIDI so that may make a difference. 
 
I have a Lenovo laptop with an i5 in it, that I use for on-site recordings and again no MIDI but it will record 8 tracks of audio without problems.  I don't do any processing of the recording files, I move them to my primary system and do whatever on that system.

If the OP is looking for a laptop primarily for tracking:
I'd take higher clock-speed over more CPU cores
Make sure the machine has low/consistent DPC Latency (important to effectively work at ultra low audio latency)
 
For tracking, I'd use an external USB3 drive... or install a high-performance drive.
A common 2.5" 5400-RPM HD is slow... compared to a high-performance 3.5" 7200-RPM HD.