The way I would do it is, I would get a hold of your product collection before it is rendered, this can be in the product list block but the collection has to be loaded. Get it as an array as so : $items = $collection->getItems()
the pass that through a custom sorting function which brings the dell products to the top, like so :
usort($items, function ($a, $b) {
if ($a->getBrand() == 'dell') return -1;
if ($b->getBrand() == 'dell') return 1;
return 0;
});
Then in the template loop through that array as normal and display the products. Here is an example of the sorting algorithm working :
https://3v4l.org/qTRGm
Note: I am using $a->getBrand()
in the example but you might need to call something else depending on your attribute´s name, but the point is to get the brand name.