Of course - with respect to Dvořák, his 'The New World' Symphony (Symphony No.9) is a great start, you can hear more modern composers in there, composers such as J.Williams and Thomas Newman. Surprisingly you can also hear where Holst may have pinched a few motifs.
Second is Jerry Goldsmith, One of my favourite modern composers. He has done themes for films like The Mummy, Airforce one, Alien, and the TV Series Star Trek - Genius. If you want, what I would consider to be, his better use of the orchestra, I would listen to the Soundtrack for Masada- I wish I could write like that.
Tchaikovsky is synonymous with works like Swan Lake and The Nutcracker; if you have ever watched any cartoons, I guarantee you will recognise these from your childhood.

There are so many many many fantastic composers out there, young and old, you only need look for them. I hope this has gone some way in helping you to fall in love with some more music.