Hi Davy,
We have checked your HTML code here and to be honest everything seems pretty much fine.
You are compressing all your CSS & JS files - that's good. Keep in mind, when you display a list of products - there is certain data you have to include on the page - and there are certain ways in which x-cart goes about generating the content on each page.
When I save your raw HTML page - it amounts to 82KB
So maybe WMT is calculating its figure on the combined weight of the page - this might include images, external JS & CSS files, etc.
Keep in mind, this is only a message - anything over 125KB may not be cached - this is fine as your are below this at 82KB.
If you take into account that your compressed CSS and JS files alone are:
CSS = 201KB
JS = 393KB
Then straight away you are above the 125KB threshold.
As you can see x-cart alone requires alot of resources to include its JS code - this alone is 3 times larger than the 125KB.
I'm not sure it's fair to blame the xtreme Gear template for exceeding the 125KB threshold that Webmaster Tools states. This is just a statement, informing you that the first 125KB will only be cached.
Nothing to worry about
regards
W.