Adjectives qualify nouns or people.
A new big wooden bed (= the bed is a noun. New, big and wooden are adjectives.)
A beautiful slim dark-haired American girl(=the girl is a people. Beuatiful, slim and dark-haired and American are adjectives.)
Attributive adjectives PRECEDE the noun or people.
clever girl(=Adjective before people.)
coloured dress(=Adjective before noun.)
big duck(=Adjective before noun.)
Predicative adjectives FOLLOW the noun or people.
The shoes look expensive (='The shoes' are the subject, 'look' is the linking verb and 'expensive' is a predicative adjective. Follow the noun.)
But if we say:
The expensive shoes (='expensive' is become to attributive adjective. There isn't linking verb. Precede the noun.)
Other example;
The lorry is broken-down (='The lorry' is the subject, 'is' is the linking verb and 'broken-down' is a predicative adjective. Follow the noun.)
But if we say:
The broken-down lorry (='broken-down' is become to attributive adjective. Precede the noun.)
Everything depends of what you want to say.
In a neutral situation, the sentence would read 'I don't have enough time...' However, the use of 'too + much' is intended to convey that there is some criticality or seriousness related to the situation. Perhaps he is cooking for his mother-in-law or he wishes to be excused on time from his work meeting, or both!
It is less formal and quite commonly used.
Best Answer
As others have pointed out, only adjectives modify nouns, and so "certain" is the correct choice to modify "brands".
However, you should also understand the difference in meaning. Despite being in the same family, certain has an additional definition that certainly does not have:
In your example, you use the third meaning of certain to mean "a particular but unspecified set" of sumptuous brands. Since certainly does not have this meaning, you would not use it.
Other examples:
Note the difference between the third example sentence and these two:
Here certain/certainly have the other meaning, "without question".