Yeah, they are harmony maniacs - and it sounds good! You should really check them out. I would like to hear your views on the band with Murray/Smith as guitarists vs. the material done with Murray/Gers. If you don't know, Smith is back in the band now, making them a triple guitar attack. So on some songs live, the harmonies sound very nice, one plays the basic melody, the second guitarist plays the same melody i.e. a 3rd above, while the last guitarist plays the same notes - but an octave higher. Very nice sounding stuff. However, often one guitar supports the bass on the rhythm, letting the two other guitarists do the harmony.
Allright, about the Iron Maiden albums. I guess The Number Of The Beast maybe is the most popular (at least most well-known) Maiden album in the 80's (probably it still is!). Another fan favourite is Powerslave, and don't forget about Seventh Son Of A Seventh Son. That's three albums with Murray and Smith on the guitars.
As you know, Janick Gers took over for Smith in 1990. That year they released the album No Prayer For The Dying. You could listen to that. Gers was doing his best to show the fans how his playing was. The next album is Fear Of The Dark. Not as raw as No Prayer, this album has more feeling I'd say. Both albums are sometimes slagged off even by the fans. That's on the Internet however.
And as a final album to check out you can't go wrong with Brave New World from 2000. That's the year Adrian Smith rejoined the band, taking with him Bruce Dickinson back in the band, to replace the one who was the Maiden vocalist from 1995-1998-99. So actually, on this album you get all three of the guitarists.
I understand that you won't buy all those albums in the nearest future, but what you could do, is check out the official Iron Maiden website, browse through the "Albums" section, and see if you can find a few songs for each of the mentioned albums. Then download a couple and give it a show. Maybe you get temped to buy them as well! You're here by warned.
Allright, that's it. Did I get carried away or did I not? I think I did.