Paint sets?

Get ready to take a hit to the wallet. About $3 to $5 a bottle.

Vallejo makes several sets (theme based) of 16 colors for about $50.

I've never seen any Model Masters or Tamiya sets. But I've never looked real hard either.

Check any of the online hobby shops.

Megahobby, Squadron, Hobbylinc, Scale Hobbyist, are some I've dealt with.

Depends what your looking for and if your using an airbrush. I have a nice set from MIG for Russian tanks designed for modulation. Vallejo make great paints and do some useful sets but very soon you'll find there are colours in there just to fill up the box and you wont use that much. Modelmaster make great paints but I only use them for very small work so wouldnt buy a set to be honest. I dont think Tamiya do sets (well I've never seen any)

No matter what building up a good collection will take a bit of cash and don't forget to buy something to store them all in, I have a box for each manufacturer to save me time looking

Pmitch

I don't see anything wrong with those Testors paint sets, except maybe they won't have the right colors.  You did not say what genre of models you build.  I regularly use Testors enamels, both the Model Master and the little rectangular bottles, and have a number of modeling friends that also use them.  I prefer enamels for slower drying and a bit more unhurried working time.

They don't have the shelf life of some other paints, but that is a tradeoff for good availability at craft stores and smaller hobby shops.

As stated above,, your best bet is to check out some online shops.