Speaking as someone who also used to do a rock show on hospital radio (1988-84), the first DT album (When Dream & Day Unite, the only one with the original singer) was a featured album on my show when it first came out.

A few bands I'd add to the list:

Mostly Autumn
Astra
Diagonal

Within Temptation (similar to Nightwish)
Epica (Likewise)
Gong
Ozric Tentacles
Darwin's Radio
Ayreon
Transatlantic (a prog supergroup comprising DT's drummer, Spock's Beard's (former) singer/keyboard player, Marillion's bass player, & Flower Kings' guitarist.  Their new album is a double & the 77-minute title track takes up the entire 1st disc!)

There are lots more where those came from, I've been a prog fan for almost 40 years & have around 500 albums (mostly prog, though not all) ;)