The names you mention are 17th-18th century Italian violin makers, BIG BUCKS to buy one. The real ones are very rare, and mostly in the hands of collectors and famous soloists. Most were based in Cremona,Italy which is still a bastison of good violin making.

You are spot on about student violins. They are a lower grade of wood, lower grade of workmanship, often machine made (instead of all hand made) and often have set up problems.Consequently, they sell more cheaply.

Each maker has his/her(?) own trademarks,such as size of the bouts, shape/position of the f holes, neck size, scroll shape, etc. Amati's and Amati copies are usually smaller all over than Strads and Guanarius, Strad usually looks more "feminine" maybe, than the Guans, but you have to be really good to tell the difference between models.